JP2014201738A - Production method of polycarbonate diol excellent in heat stability - Google Patents

Abstract

An object of the present invention relates to a method for producing a polycarbonate diol which is less colored during the preparation of a polycarbonate diol raw material, a polycondensation reaction, and a purification process, and which has excellent thermal stability. A method for producing a polycarbonate diol having a number average molecular weight of 250 or more and 5500 or less by subjecting a dihydroxy compound and a carbonate compound to a transesterification reaction using a transesterification catalyst. / Or in the presence of phosphorous acid, and the total amount of phosphoric acid and phosphorous acid is 0.05 mol times or more and 0.9 mol times or less with respect to 1 mol of the transesterification catalyst A method for producing a diol. [Selection figure] None

Description

  The present invention relates to a method for producing a polycarbonate diol having excellent thermal stability. Specifically, the present invention relates to a method for producing a polycarbonate diol having a good color tone and excellent thermal stability.

  Polycarbonate diol is used as a raw material for polyurethane and urethane acrylate, but if the raw material polycarbonate diol is colored, the polyurethane produced from this polycarbonate diol will also be colored, reducing the commercial value. Reduction of coloring is also desired for diols. In addition, when the molecular weight increases or the composition changes due to heating, the physical properties of the polyurethane change when it is made of polyurethane or the like.

Patent Document 1 proposes that an organophosphate compound be added to an aliphatic polycarbonate diol for thermal stabilization.
Patent Document 2 discloses that a polycarbonate polyol is produced in the presence of a Bronsted acid or phosphoric acid compound.

  Patent Document 3 discloses that an antioxidant is added to polycarbonate polyol or the like for stabilization against thermal decomposition.

JP 61-151263 A JP 2000-95854 A Special table 2008-531801 gazette

  In the known technology, when producing polycarbonate diol using dihydroxy compound as a monomer component, these dihydroxy compounds have low polymerization reactivity, so harsh conditions such as increasing the amount of catalyst and increasing the polymerization temperature are selected. There was a need to do. Therefore, the polycarbonate diol produced under these conditions has a problem that it is colored or inferior in thermal stability.

  When a highly reactive catalyst is selected, there is a problem of coloring due to side reactions, although the reaction rate increases.

Furthermore, when the polycarbonate diol having the above-mentioned problems is used as a raw material for the polycarbonate-based polyurethane, there is a risk of causing coloration during the polyurethane-forming reaction, deterioration of the thermal stability of the polyurethane, and color change due to heating. .
In order to solve these problems, attempts have been made to add a phosphorus compound during the polymerization reaction in order to reduce the coloration of the polycarbonate diol, but this is not sufficient.
An object of the present invention is to provide a method for producing a polycarbonate diol, which efficiently produces a polycarbonate diol with little coloration and excellent thermal stability.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the following inventions meet the above-mentioned object and have completed the present invention.
That is, the gist of the present invention is as follows.
[1]
A method for producing a polycarbonate diol having a number average molecular weight of 250 or more and 5500 or less by subjecting a dihydroxy compound and a carbonate compound to an ester exchange reaction using an ester exchange catalyst.
The transesterification reaction is performed in the presence of phosphoric acid and / or phosphorous acid, and the total amount of phosphoric acid and phosphorous acid is 0.05 mol times or more and 0.9 mol times with respect to 1 mol of the transesterification catalyst. A method for producing a polycarbonate diol, characterized by:
[2]
[1] The transesterification catalyst is a compound of at least one element selected from the group consisting of long-period periodic table group 1 elements (excluding hydrogen) and long-period periodic table group 2 elements. A process for producing a polycarbonate diol.
[3]
The method for producing a polycarbonate diol according to [1] or [2], wherein the transesterification catalyst is added to a mixture of the dihydroxy compound, the carbonate compound, and phosphoric acid and / or phosphoric acid, and a transesterification reaction is performed.
[4]
The method for producing a polycarbonate diol according to any one of [1] to [3], wherein the transesterification catalyst amount is 1 μmol to 200 μmol with respect to 1 mol of the dihydroxy compound.
[5]
The method for producing a polycarbonate diol according to any one of [1] to [4], wherein the carbonate compound is diaryl carbonate.
[6]
With the progress of the transesterification reaction, the ratio of the terminal group derived from the carbonate compound out of the total molecular chain terminals of the polycarbonate diol becomes 10 mol% or less, and then the polycarbonate diol is further added with phosphoric acid and / or phosphorous acid. The method for producing a polycarbonate diol according to any one of [1] to [5], which further comprises a purification step.
[7]
A polycarbonate diol produced by the method for producing a polycarbonate diol according to any one of [1] to [6], wherein the turbidity measured with an integrating sphere turbidimeter is 2.0 ppm or less. Polycarbonate diol.
[8]
A polycarbonate diol produced by the method for producing a polycarbonate diol according to any one of [1] to [6], wherein the Hazen color number measured according to JIS K0071-1 (1998) is 60 or less. A polycarbonate diol characterized by that.

  According to the method for producing a polycarbonate diol of the present invention, coloring of the polycarbonate diol can be suppressed in the raw material preparation, the transesterification reaction, and the purification step, and furthermore, a polycarbonate diol having excellent thermal stability can be efficiently produced. .

  Hereinafter, although the form of this invention is demonstrated in detail, this invention is not limited to the following embodiment, Various deformation | transformation can be implemented within the range of the summary.

[1. Production method of polycarbonate diol]
The method for producing a polycarbonate diol of the present invention is a method for producing a polycarbonate diol having a number average molecular weight of 250 or more and 5500 or less by subjecting a dihydroxy compound and a carbonate compound to an ester exchange reaction using an ester exchange catalyst.
The reaction is carried out in the presence of phosphoric acid and / or phosphorous acid, and the total amount of phosphoric acid and phosphorous acid is 0.05 mol times or more and 0.9 mol times or less with respect to 1 mol of the transesterification catalyst. This is a method for producing a polycarbonate diol.

<1-1. Dihydroxy Compound>
The dihydroxy compound is not particularly limited, but it preferably contains a compound represented by the following formula (A) (hereinafter sometimes referred to as “dihydroxy compound (A)”).
When a polycarbonate diol is produced using a dihydroxy compound containing the dihydroxy compound (A) as a raw material monomer, phosphoric acid and phosphorous acid are used in the transesterification reaction with a transesterification catalyst in the presence of phosphoric acid and / or phosphorous acid. When the total amount is a specific amount, coloring can be further suppressed and a polycarbonate diol having excellent thermal stability can be obtained.

  Examples of the dihydroxy compound (A) include 2,2-dimethyl-1,3-propanediol (hereinafter, sometimes abbreviated as “nepentyl glycol”, “NPG”), 2-ethyl-2-butyl-1,3. -2,2-dialkyl-substituted 1,3-propanediols (hereinafter 2), such as propanediol, 2,2-diethyl-1,3-propanediol and 2-pentyl-2-propyl-1,3-propanediol 2,2-dialkyl-1,3-propanediol, where the alkyl group is an alkyl group having 15 or less carbon atoms), 2,2,4,4-tetramethyl-1,5- Tetraalkyl-substituted alkylene diols such as pentanediol and 2,2,9,9-tetramethyl-1,10-decanediol, 3,9-bis (1,1-dimethyl) Ru-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane-containing diols, 2,2-diphenyl-1,3-propanediol, 2,2 -Divinyl-1,3-propanediol, 2,2-diethynyl-1,3-propanediol, 2,2-dimethoxy-1,3-propanediol, bis (2-hydroxy-1,1-dimethylethyl) ether Bis (2-hydroxy-1,1-dimethylethyl) thioether, 2,2,4,4-tetramethyl-3-cyano-1,5-pentanediol, and the like.

(In the above formula, n is 0 or 1, R ₁ and R ₂ are each independently a group selected from the group consisting of an alkyl group having 1 to 15 carbon atoms, an aryl group, an alkenyl group, an alkynyl group and an alkoxy group, In the range of the number of carbon atoms, an oxygen atom, a sulfur atom, a nitrogen atom, a halogen atom, or a substituent containing these may be present, and X is a C 1-15 divalent divalent carbon atom that may contain a hetero atom. Represents a group.)

Among these, those in which n is 0, R ₁ and R ₂ are alkyl groups having 1 to 5 carbon atoms are preferable. Specific raw material compounds that give the structure include, for example, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2-diethyl-1, 2,2-dialkyl substituted 1,3-propanediols such as 3-propanediol and 2-pentyl-2-propyl-1,3-propanediol.

  The dihydroxy compound is not particularly limited, but preferably contains a dihydroxy compound having a site represented by the following formula (B) (hereinafter sometimes referred to as “dihydroxy compound (B)”).

(However, the case where the site represented by the formula (B) is a part of —CH ₂ —O—H is excluded.)
When a polycarbonate diol is produced using a dihydroxy compound containing the dihydroxy compound (B) as a raw material monomer, phosphoric acid and phosphorous acid are used in the transesterification reaction with a transesterification catalyst in the presence of phosphoric acid and / or phosphorous acid. When the total amount is a specific amount, coloring can be further suppressed and a polycarbonate diol having excellent thermal stability can be obtained.

  More specific examples of the dihydroxy compound (B) include oxyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9 , 9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis (4 -(2-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butylphenyl) fluorene, 9,9-bis (4- (2- Hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9,9 Bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3,5-dimethylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene 9,9-bis (4- (3-hydroxy-2,2-dimethylpropoxy) phenyl) fluorene, etc., an aromatic group in the side chain And a compound having an ether group bonded to an aromatic group in the main chain and a compound having a cyclic ether structure. Among compounds having a cyclic ether structure, compounds having a plurality of cyclic ether structures are more preferable, and compounds having two cyclic ether structures are more preferable. As the compound having a cyclic ether structure, an anhydrous sugar alcohol represented by a dihydroxy compound represented by the following formula (C) is particularly preferable. These may be used alone or in combination of two or more depending on the required performance of the polycarbonate diol obtained.

Among these dihydroxy compounds, it is preferable to use a dihydroxy compound having no aromatic ring structure from the viewpoint of the light resistance of polyurethane obtained from polycarbonate diol. Among them, there are various abundantly available as plant-derived resources. Isosorbide (hereinafter sometimes abbreviated as “ISB”) obtained by dehydrating and condensing sorbitol produced from starch is easy to obtain and manufacture, hardness, abrasion resistance, light resistance, carbon neutral From the viewpoint of

As long as the effects of the present invention are not impaired, dihydroxy compounds other than the dihydroxy compound (A) and the dihydroxy compound (B) (sometimes referred to as other dihydroxy compounds) may be used for the polycarbonate diol of the present invention. Other dihydroxy compounds include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octane Linear terminal diols such as diol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol and 1,20-eicosanediol, diethylene glycol, Diols having ether groups such as ethylene glycol, tetraethylene glycol and polytetramethylene glycol, thioether diols such as bishydroxyethyl thioether, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propane Diol, 3-methyl-1 Branched diols such as 5-pentanediol and 2,4-diethyl-1,5-pentanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4, 4-dicyclohexyldimethylmethanediol, 2,2'-bis (4-hydroxycyclohexyl) propane, 1,4-dihydroxyethylcyclohexane, isosorbide, 2,5-bis (hydroxymethyl) tetrahydrofuran, 4,4'-isopropylidenedi Diols having a cyclic group in the molecule such as cyclohexanol and 4,4′-isopropylidenebis (2,2′-hydroxyethoxycyclohexane), nitrogen-containing diols such as diethanolamine and N-methyl-diethanolamine, and bis (hydroxy Chill) sulfur-containing diols such as Suruhido, and the like can be given. These diols may be used alone as the component (B), or may be used in combination.

<1-2. Carbonate compound>
The carbonate compound that can be used is not limited as long as the effects of the present invention are not impaired, and examples thereof include dialkyl carbonate, diaryl carbonate, and alkylene carbonate. Of these, diaryl carbonate is preferred from the viewpoint of reactivity.

  Specific examples of the carbonate compound that can be used in the method for producing a polycarbonate diol of the present invention include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate, ethylene carbonate, and the like. Diphenyl carbonate (hereinafter abbreviated as “DPC”). Is preferred).

<1-3. Use ratio of raw material monomer>
The amount of the carbonate compound used is not particularly limited, but the lower limit is preferably 0.35, more preferably 0.50, even more preferably 0.60, and the upper limit is a molar ratio with respect to a total of 1 mol of dihydroxy compounds. Preferably it is 1.00, More preferably, it is 0.98, More preferably, it is 0.97. If the amount of the carbonate compound used exceeds the above upper limit, the proportion of the polycarbonate diol end group that is not a hydroxyl group may increase or the molecular weight may not fall within the predetermined range. If the amount is less than the lower limit, the polymerization does not proceed to the predetermined molecular weight. There is a case.

<1-4. Transesterification Catalyst>
In the method for producing a polycarbonate diol of the present invention, a transesterification catalyst (hereinafter sometimes referred to as “catalyst”) is used.
As the transesterification catalyst, any compound that is generally considered to have transesterification ability can be used without limitation.

  Examples of transesterification catalysts include compounds of long-period periodic table group 1 elements (excluding hydrogen) such as lithium, sodium, potassium, rubidium and cesium; long-periodic periods such as magnesium, calcium, strontium and barium Table 2 Group element compounds; Long Periodic Periodic Table Group 4 element compounds such as titanium and zirconium; Long Periodic Table 5 Group element compounds such as hafnium; Long Periodic Periodic Table 9 such as cobalt Group element compound; Long period type periodic table group 12 element compound such as zinc; Long period type periodic table group 13 element compound such as aluminum; Long period type periodic table group 14 such as germanium, tin, lead, etc. Compound of element; Compound of group 15 element of long-period type periodic table such as antimony and bismuth; Conversion of lanthanide metal such as lanthanum, cerium, europium, ytterbium Thing, and the like. Among these, from the viewpoint of increasing the transesterification reaction rate, long-period periodic table group 1 elements (excluding hydrogen) long-period periodic table group 2 elements, long-period periodic table group 4 elements, long-period elements Group consisting of Group 5 element of long-period type periodic table, Group 9 element of long-period type periodic table, Group 12 element of long-period type periodic table, Group 13 element of long-period type periodic table and Group 14 element of long-period type periodic table A compound of at least one element selected from the group consisting of a long-period periodic table group 1 element (excluding hydrogen) and a long-period periodic table group 2 element. The compound of the long period type periodic table group 2 element is more preferable.

  Among the compounds of group 1 elements of the long-period type periodic table (excluding hydrogen), lithium, potassium, and sodium compounds are preferable, lithium and sodium compounds are more preferable, and sodium compounds are more preferable. Among the compounds of Group 2 elements of the long-period type periodic table, compounds of magnesium, calcium and barium are preferable, compounds of calcium and magnesium are more preferable, and compounds of magnesium are more preferable. These metal compounds are mainly used as hydroxides and salts. Examples of salts when used as a salt include halide salts such as chloride, bromide and iodide; carboxylates such as acetate, formate and benzoate; methanesulfonic acid, toluenesulfonic acid and trifluoro Examples thereof include sulfonates such as romethanesulfonic acid; phosphorus-containing salts such as phosphates, hydrogen phosphates, and dihydrogen phosphates; acetylacetonate salts. The catalyst metal can also be used as an alkoxide such as methoxide or ethoxide.

  Among these, preferably, an acetate, nitrate, sulfate, carbonate, phosphate, hydroxide, halide, alkoxide of at least one metal selected from Group 2 elements of the long-period type periodic table is used. More preferably, long-period periodic table group 2 element acetates, carbonates and hydroxides are used, and magnesium, calcium acetates, carbonates and hydroxides are more preferably used. Preferably, magnesium and calcium acetate are used, and most preferably magnesium acetate is used.

The amount of the catalyst used is usually 1 μmol to 200 μmol, and the lower limit is preferably 5 μmol, more preferably 10 μmol, and even more preferably 15 μmol per 1 mol of all dihydroxy compounds used. Molar times. The upper limit is preferably 100 μmol times, more preferably 70 μmol times, and even more preferably 50 μmol times. If the amount of the catalyst used is too small, sufficient polymerization activity cannot be obtained and the progress of the polymerization reaction is slowed down, so that it is difficult to obtain a polycarbonate diol having a desired molecular weight, not only the production efficiency is lowered, but also the raw material monomer is polymerized. During the reaction, the time remaining in the system in an unreacted state becomes long, so that the color tone may be deteriorated. In addition, the amount of monomer distilling with the by-produced monohydroxy compound increases, and as a result, the raw material basic unit may be deteriorated and extra energy may be required for its recovery. In the case of copolymerization using a compound, the composition ratio of the monomer used as the raw material and the composition ratio of the constituent monomer units in the product polycarbonate diol may change. On the other hand, if the amount of catalyst used is too large, an excessive amount of catalyst may remain after the transesterification reaction, and the polycarbonate diol may become cloudy or may be easily colored by heating. Moreover, when manufacturing a polyurethane, reaction may be inhibited or reaction may be accelerated | stimulated too much.

  For this reason, the amount of catalyst remaining in the polycarbonate diol is not particularly limited, but is preferably 0.1 ppm or more, more preferably 0.5 ppm or more, still more preferably 1 ppm or more, and particularly preferably 2 ppm as the content in terms of catalyst metal. Above, most preferably 3 ppm or more. Moreover, 100 ppm or less is preferable, More preferably, it is 50 ppm or less, More preferably, it is 30 ppm or less, Especially preferably, it is 20 ppm or less, Most preferably, it is 10 ppm or less.

<1-5. Molecular Weight / Molecular Weight Distribution>
The lower limit of the number average molecular weight (Mn) obtained from the nuclear magnetic resonance (NMR) of the polycarbonate diol produced by the production method of the present invention is 250, preferably 500, more preferably 750. On the other hand, the upper limit is 5,500, preferably 4,500, more preferably 3,500, and still more preferably 3,000. If the Mn of the polycarbonate diol is less than the lower limit, sufficient flexibility may not be obtained when urethane is used. On the other hand, if the upper limit is exceeded, the viscosity increases, and handling during polyurethane formation may be impaired.

<1-6. Molecular chain end>
The molecular chain terminal of the polycarbonate diol produced by the production method of the present invention is mainly a hydroxyl group. However, in the case of a polycarbonate diol obtained by the reaction of a dihydroxy compound and a carbonate compound, there is a possibility that some molecular chain terminals are not hydroxyl groups as impurities. As specific examples thereof, the molecular chain terminal is an alkyloxy group or an aryloxy group, and many have a structure derived from a carbonate compound.

For example, when diphenyl carbonate is used as the carbonate compound, phenoxy group (PhO-) is used as the aryloxy group, methoxy group (MeO-) is used as the alkyloxy group when dimethyl carbonate is used, and ethoxy group is used when diethyl carbonate is used. (EtO-), when using ethylene carbonate which may hydroxyethoxy group _(HOCH 2 _CH 2 O-) remains as a molecular chain terminal (here, Ph represents a phenyl group, Me represents a methyl group Et represents an ethyl group).

In the molecular chain terminal of the polycarbonate diol, the ratio of the total number of terminals derived from the dihydroxy compound with respect to the total number of terminals is preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 97. The mol% or more, particularly preferably 99 mol% or more. By setting the amount within the above range, it becomes easy to obtain a desired molecular weight when polyurethane is used, and it becomes possible to become a polyurethane raw material having an excellent balance of physical properties.
The ratio of the number of terminal groups in which the molecular chain terminal of the polycarbonate diol is derived from the carbonate compound is preferably 10 mol% or less, more preferably 5 mol% or less, and still more preferably 3 mol%, based on the total number of terminals. Hereinafter, it is particularly preferably 1 mol% or less.

The lower limit of the hydroxyl value of the polycarbonate diol is preferably 20 mg-KOH / g, more preferably 25 mg-KOH / g, still more preferably 30 mg-KOH / g, and most preferably 35 mg-KOH / g. Moreover, an upper limit becomes like this. Preferably it is 450 mg-KOH / g, More preferably, it is 230 mg-KOH / g, More preferably, it is 150 mg-KOH / g. If the hydroxyl value is less than the above lower limit, the viscosity may be too high and handling during polyurethane formation may be difficult. If the upper limit is exceeded, physical properties such as flexibility and low-temperature characteristics may be insufficient when polyurethane is used.

<1-7. Phosphoric acid, phosphorous acid>
In the method for producing a polycarbonate diol of the present invention, the transesterification catalyst is carried out in the presence of phosphoric acid and / or phosphorous acid. The total amount of phosphoric acid and phosphorous acid is 0.05 mol times or more and 0.9 mol times or less with respect to 1 mol of the transesterification catalyst. The upper limit of the total amount is preferably 0.7 mol times, more preferably 0.5 mol times, still more preferably 0.3 mol times, and the lower limit is preferably 0.07 mol times, more preferably 0.1 mol times. Double, more preferably 0.2 mole times. When the total amount of phosphoric acid and phosphorous acid exceeds the upper limit, the reactivity in the transesterification reaction may be lowered. Moreover, if it is less than the said minimum, the coloring inhibitory effect is low and polycarbonate diol may color.

  It is preferable to add a transesterification catalyst after phosphoric acid and / or phosphorous acid is contained in the transesterification reaction system. That is, it is preferable to add a transesterification catalyst after preparing the mixture of the dihydroxy compound, the carbonate compound, and phosphoric acid and / or phosphoric acid. For example, when a dihydroxy compound and a carbonate compound are heated and melted to form a mixture, the transesterification reaction may proceed even if there is no transesterification catalyst. In particular, if the carbonate compound is diphenyl carbonate, the transesterification reaction may occur. Progress is remarkable. In addition, when the holding time of the mixture is long, it becomes easy to color. In this case, even if there is no transesterification catalyst in the mixture, the presence of phosphoric acid and / or phosphorous acid suppresses the transesterification reaction, reduces the coloration, and makes the polycarbonate diol stable in quality. Is possible.

  As the transesterification proceeds, the proportion of terminal groups derived from the carbonate compound among the total molecular chain terminals of the polycarbonate diol produced decreases. And after the ratio of the terminal group derived from a carbonate compound becomes 10 mol% or less with respect to the total molecular chain terminal group amount, phosphoric acid and / or phosphorous acid are preferable with respect to 1 mol of transesterification catalysts. Is preferably added in an amount of 0.1 mol times to 50 mol times. As for the addition timing of phosphoric acid and / or phosphorous acid, the proportion of the terminal group derived from the carbonate compound is more preferably 5 mol% or less, further preferably 3% or less, and particularly preferably 1% or less.

  The lower limit of the addition amount of phosphoric acid and / or phosphorous acid is more preferably 0.3 mol times, more preferably 0.4 mol times, particularly preferably 0.5 mol times, especially 0.5 mol times, with respect to 1 mol of the transesterification catalyst. Preferably it is 0.6 mol times, Most preferably, it is 0.7 mol times. The upper limit is more preferably 10 molar times, further preferably 5 molar times, particularly preferably 3 molar times, particularly preferably 2 molar times, and most preferably 1.5 molar times. By being in the said range, it becomes possible to deactivate a transesterification catalyst efficiently. Therefore, when removing residual monomers and adjusting the molecular weight after the transesterification reaction, it is possible to produce a polycarbonate diol with stable quality without coloration or molecular weight change due to heating.

In the case where phosphoric acid and / or phosphorous acid is added after the ratio of terminal groups derived from the carbonate compound is 10 mol% or less with respect to the total amount of terminal groups, the transesterification catalyst 1 used for the production of the polycarbonate diol Preferably, it is added to the reaction apparatus in an amount of 0.1 mol times or more and 50 mol times or more per mol. The addition can be performed even at room temperature, but the effect is more efficient when heat-treated. The temperature of this heat treatment is not particularly limited, but the upper limit is preferably 150 ° C., more preferably 120 ° C., still more preferably 100 ° C., and the lower limit is preferably 50 ° C., more preferably 60 ° C., even more preferably. Is 70 ° C. If the temperature is lower than this, the effect may be insufficiently exhibited. On the other hand, at temperatures exceeding 150 ° C., the obtained polycarbonate diol may be colored by heat.
The time for reacting with phosphoric acid and / or phosphorous acid is not particularly limited, but it is usually 0.
1 to 5 hours.

  By containing phosphoric acid and / or phosphorous acid, color tone deterioration due to heating during raw material preparation and transesterification can be suppressed, and phosphoric acid and / or phosphorous acid is added to convert the transesterification catalyst. By deactivation, coloring, molecular weight, and composition change due to subsequent heating can be suppressed. Among these, phosphoric acid is more preferable from the viewpoints of suppressing the deterioration of the color tone of the polycarbonate diol and having less influence on the reactivity and color tone at the time of polyurethane formation.

<1-8. Turbidity>
The turbidity of the polycarbonate diol produced by the production method of the present invention was measured by adding a 50% methylene chloride solution of polycarbonate diol to a 10 mm cell using an integrating sphere turbidimeter PT-200 manufactured by Mitsubishi Chemical Corporation. Is preferably 2.0 ppm or less, more preferably 1.0 ppm or less, and particularly preferably 0.5 ppm or less. When the turbidity is larger than 2.0 ppm, the transparency of polyurethane obtained using polycarbonate diol as a raw material may be deteriorated, and the commercial value may be lowered, or the mechanical properties may be lowered. Turbidity is thought to be mainly caused by aggregation / precipitation of catalyst components, aggregation / precipitation of additives, and cyclic oligomers with low solubility. To reduce the turbidity to 2.0 ppm or less, It is necessary to comprehensively control the concentration of the monohydroxy compound and the concentration of the unreacted monomer during the transesterification reaction and after the end of the transesterification reaction. For example, if the solubility of the catalyst itself in polycarbonate diol is low, the catalyst is likely to precipitate, and if the concentration is high, the precipitation is promoted. On the other hand, in order to suppress the formation of cyclic oligomers having poor solubility, selection and combination of dihydroxy compounds as monomers are also important. For example, in the case of a homopolymer, a cyclic oligomer tends to be generated, but by copolymerization, it becomes difficult to obtain a stable cyclic structure, and the turbidity tends to decrease. Further, if the temperature during the production of the polycarbonate diol is high, a cyclic oligomer is likely to be generated thermodynamically, so it is effective to lower the polymerization temperature. However, if the amount is too low, productivity may be hindered, excessive time may be required, and the color tone may be deteriorated or the turbidity may be deteriorated.

<1-9. APHA value>
The color of the polycarbonate diol produced by the production method of the present invention is 60 or less in terms of the value (hereinafter referred to as “APHA value”) represented by the Hazen color number (based on JIS-K0071-1: 1998). Preferably, it is 50 or less, more preferably 30 or less, and particularly preferably 20 or less. When the APHA value exceeds 60, the color tone of polyurethane obtained using polycarbonate diol as a raw material is deteriorated, and the commercial value is lowered or the thermal stability is deteriorated. In order to reduce the APHA value to 60 or less, the catalyst at the time of producing the polycarbonate diol, the selection of the type and amount of the additive, the thermal history, the concentration of the monohydroxy compound during the transesterification reaction and after the transesterification reaction, and the unreacted monomer It is necessary to comprehensively control the concentration of. Further, light shielding during the transesterification reaction and after completion of the transesterification reaction is also effective. It is also important to set the molecular weight of the polycarbonate diol and to select the dihydroxy compound species that is a monomer. Polycarbonate diols made from aliphatic dihydroxy compounds having alcoholic hydroxyl groups as raw materials show various excellent performances such as flexibility, water resistance, and light resistance when processed into polyurethane, but aromatic dihydroxy compounds are used as raw materials. The heat history and the coloration due to the catalyst tend to be remarkably higher than in the case of the above, and it is not easy to make the APHA value 60 or less.

<1-10. Residual monomers, etc.>
For example, when an aromatic carbonate compound such as diphenyl carbonate is used as a raw material, phenols are by-produced during the production of the polycarbonate diol. Since phenols are monofunctional compounds, for example, when polyurethane is produced using the polycarbonate diol as a raw material, the phenols may be an inhibitor of the reaction, and the urethane bond formed by the phenols is Since the bonding force is weak, it is dissociated by heat in the subsequent steps, etc., and there is a possibility that the isocyanate and phenols are regenerated and cause problems. Moreover, since phenols are also stimulating substances, it is preferable that the residual amount of phenols in the polycarbonate diol is small. Specifically, the weight ratio with respect to the polycarbonate diol is preferably 1000 ppm or less, more preferably 500 ppm or less, still more preferably 300 ppm or less, and particularly preferably 100 ppm or less. In order to reduce the phenols in the polycarbonate diol, as described later, the pressure of the transesterification reaction of the polycarbonate diol is set to a high vacuum of 1 kPa or less as an absolute pressure, or a purification process such as thin film distillation after the transesterification reaction of the polycarbonate diol It is effective to do.

  In the polycarbonate diol, the carbonate compound used as a raw material during production may remain. The remaining amount of the carbonate compound in the polycarbonate diol is not limited, but a smaller amount is preferable, and the upper limit of the weight ratio with respect to the polycarbonate diol is preferably 5% by weight, more preferably 3% by weight, still more preferably 1% by weight. is there. If the carbonate compound content of the polycarbonate diol is too large, the reaction during polyurethane formation may be inhibited. On the other hand, the lower limit is not particularly limited, but is preferably 0.1% by weight, more preferably 0.01% by weight, and still more preferably 0% by weight.

  In polycarbonate diol, the dihydroxy compound used at the time of manufacture may remain. The residual amount of the dihydroxy compound in the polycarbonate diol is not limited, but a smaller amount is preferable, and the weight ratio with respect to the polycarbonate diol is preferably 1% by weight or less, more preferably 0.1% by weight or less, and still more preferably. Is 0.05% by weight or less. If the residual amount of the dihydroxy compound in the polycarbonate diol is large, the molecular length of the soft segment portion when polyurethane is used may be insufficient, and desired physical properties may not be obtained.

  In polycarbonate diol, the cyclic carbonate (cyclic oligomer) byproduced in the case of manufacture may be contained. For example, when 2,2-dimethyl-1,3-propanediol is used as the dihydroxy compound (A), 2,2-dimethyl-1,3-dioxan-2-one or more of these two or more molecules are cyclic. A carbonate or the like may be produced and contained in the polycarbonate diol. These compounds may cause side reactions in the polyurethane-forming reaction and cause turbidity. Therefore, the pressure of the transesterification reaction of the polycarbonate diol is set to a high vacuum of 1 kPa or less as an absolute pressure, It is preferable to remove as much as possible by performing thin film distillation after the synthesis. The content of these cyclic carbonates contained in the polycarbonate diol is not limited, but is preferably 3% by weight or less, more preferably 1% by weight or less, and still more preferably 0.5% by weight or less as a weight ratio to the polycarbonate diol. .

<1-11. Reaction temperature>
The reaction temperature in the transesterification reaction can be arbitrarily adopted as long as a practical reaction rate can be obtained. Usually, the lower limit of the reaction temperature is preferably 70 ° C, more preferably 100 ° C, and further preferably 130 ° C. The upper limit of the reaction temperature is usually preferably 250 ° C, more preferably 230 ° C, and further preferably 200 ° C. By setting the upper limit of the reaction temperature to the above value, it is possible to prevent quality problems such as coloring of the obtained polycarbonate diol and formation of an ether structure.

  Furthermore, the reaction temperature is preferably 180 ° C. or lower, more preferably 170 ° C. or lower, and even more preferably 160 ° C. or lower throughout the entire ester exchange reaction for producing polycarbonate diol. By setting the reaction temperature to 180 ° C. or lower throughout all the steps, it is possible to prevent the color from being easily colored depending on conditions.

<1-12. Amount of hydroxyaryl during reaction>
In the polycarbonate diol, the content of hydroxyaryl such as phenol usually contained in the solution during the reaction is preferably 45% by weight or less, more preferably 30% by weight or less, and further preferably 20% by weight or less. preferable.

In particular, it is preferable to maintain the content of phenols contained in the solution during the reaction throughout the transesterification reaction below the upper limit. By making it below the upper limit, the amount of phenols can be limited under high temperature conditions during the transesterification reaction, and it becomes difficult to color.
In addition, as a method of making content of phenol below an upper limit, for example, it reacts under reduced pressure from the reaction initial stage, Distilling off the produced | generated phenols etc. is mentioned.

  The content of the phenols can be measured by, for example, extracting a part of the reaction solution from the reactor at regular intervals and quantifying it with NMR and liquid chromatography.

<1-13. Reaction pressure>
Although the reaction can be carried out at normal pressure, the transesterification reaction is an equilibrium reaction, and the reaction can be biased toward the production system by distilling off the light-boiling components produced out of the system. Therefore, usually, in the latter half of the reaction, it is preferable to carry out the reaction while distilling off the light-boiling components under reduced pressure conditions.

Or it is also possible to make it react, distilling off the light boiling component produced | generated by reducing pressure gradually from the middle of reaction. In particular, it is preferable to increase the degree of vacuum at the end of the reaction because the by-produced monoalcohol, phenols and cyclic carbonate can be distilled off.
In this case, the upper limit of the reaction pressure at the end of the reaction is preferably 10 kPa, more preferably 5 kPa, and further preferably 1 kPa. In order to effectively distill these light-boiling components, the reaction can be carried out while flowing an inert gas such as nitrogen, argon and helium through the reaction system.

In the case of using a low-boiling dihydroxy compound or carbonate compound in the transesterification reaction, the reaction is initially performed near the boiling point of the dihydroxy compound or carbonate compound, and the temperature is gradually raised as the reaction proceeds. A method of allowing the reaction to proceed can also be employed. In this case, the unreacted carbonate compound can be prevented from being distilled off at the initial stage of the reaction, which is preferable.
Furthermore, in order to prevent the distillation of these raw materials, it is possible to carry out the reaction while refluxing the dihydroxy compound and the carbonate compound by attaching a reflux tube to the reactor. In this case, the charged raw materials are not lost. This is preferable because the ratio can be accurately adjusted.

<1-14. Reaction method>
The transesterification reaction can be carried out batchwise or continuously. In the present invention, it is preferred to carry out the transesterification continuously in view of the stability of the product. The apparatus to be used may be any of a tank type, a tube type and a tower type, and a known polymerization tank equipped with various stirring blades can be used. The atmosphere during the temperature rise of the apparatus is not particularly limited, but from the viewpoint of product quality, it is preferably carried out in an inert gas such as nitrogen gas under normal pressure or reduced pressure.

<1-15. Purification process>
It is preferable to add a phosphoric acid and / or phosphorous acid to the polycarbonate diol and then have a purification step. The purification step is to purify the raw material dihydroxy compound, raw material carbonate compound, light-boiling cyclic carbonate by-product, alcohols by-produced from the carbonate compound, phenols and added catalyst in the polycarbonate diol product. Examples of the process include vacuum distillation, steam distillation, and thin film distillation, and thin film distillation is particularly effective.

Although there is no restriction | limiting in particular as thin film distillation conditions, As for the temperature at the time of thin film distillation, it is preferable that an upper limit is 250 degreeC, and it is preferable that it is 200 degreeC. Moreover, it is preferable that a minimum is 120 degreeC, and it is more preferable that it is 150 degreeC.
By setting the lower limit of the temperature at the time of thin-film distillation to the above value, the effect of removing light boiling components becomes sufficient. Further, by setting the upper limit to 250 ° C., it is possible to prevent the polycarbonate diol obtained after thin film distillation from being colored.

The upper limit of the pressure during thin film distillation is preferably 500 Pa, more preferably 150 Pa, and even more preferably 50 Pa. By setting the pressure during thin film distillation to the upper limit value or less, a light boiling component removal effect can be sufficiently obtained.
Moreover, the upper limit of the temperature of the polycarbonate diol just before thin film distillation is preferably 250 ° C, and more preferably 150 ° C. Moreover, it is preferable that a minimum is 80 degreeC, and it is more preferable that it is 120 degreeC.

By setting the temperature for keeping the polycarbonate diol just before the thin film distillation to the lower limit or more, it is possible to prevent the flowability of the polycarbonate diol just before the thin film distillation from being lowered. On the other hand, by setting it to the upper limit or less, it is possible to prevent the polycarbonate diol obtained after thin film distillation from being colored.
Further, in order to remove water-soluble impurities, it may be washed with water, alkaline water, acidic water, a chelating agent solution or the like. In that case, the compound to be dissolved in water can be arbitrarily selected.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
Below, the evaluation method of each physical property value is as follows.
[Evaluation method: Polycarbonate diol]

<Quantification of phenoxy group content, dihydroxy compound content and phenol content by NMR and measurement of number average molecular weight of polycarbonate diol>
Polycarbonate diol was dissolved in CDCl ₃ , 400 MHz ¹ H-NMR (AL-400 manufactured by JEOL Ltd.) was measured, phenoxy group, dihydroxy compound, and phenol were identified from the signal position of each component, and each integrated value was determined. The content of was calculated. In this case, the lower detection limit is 100 ppm as the weight of phenol with respect to the weight of the entire sample, and 0.1% by weight of the dihydroxy compound. The ratio of the phenoxy group is determined from the ratio of the integrated value of one proton of the phenoxy group to the integrated value of one proton of the entire terminal, and the detection limit of the phenoxy group is 0.1% with respect to the entire terminal. is there. The number average molecular weight of the polycarbonate diol was calculated from the integral value of the polycarbonate.
Each integral value was calculated according to the following chemical shift. Note that the chemical shift value may vary slightly depending on the composition. In this case, the method of taking the integral value may be changed as appropriate.

[Composition analysis (ISB / 1,6-hexanediol copolymer polycarbonate diol)]
The integral value of the chemical shift value was obtained by the ¹ H-NMR. 1,6 hexanediol may be abbreviated as “16HD”.
Integral value of δ 5.207 to 4.973 ppm = a
Integral value of δ 4.697 to 4.599 ppm = b
Integral value of δ4.599 to 4.464 ppm = c
Integral value of δ 3.686 to 3.501 ppm = d
Integral value of δ2.764-2.717 ppm = e
Integral value of δ 1.493 to 1.295 ppm = f
There are two types of structures of chain ends derived from ISB, which are referred to as “ISB end 1” and “ISB end 2”, respectively. Further, the ISB-derived structure portion in the polycarbonate diol other than the terminal is referred to as “in ISB”. Similarly, regarding 16HD, “16HD end” and “16HD medium” are set. Considering the number of each proton, calculate the number according to the following formula.
(ISB) Terminal 1 = be
(ISB) middle = c- (ISB) terminal 1
(ISB) terminal 2 = a- (ISB) terminal 1- (ISB) medium × 2
(16HD) terminal = (d-e- (ISB) terminal 1) / 2
(16HD) medium = (f− (16HD) terminal × 4) ÷ 4

[Composition analysis (NPG / 16HD copolymer polycarbonate diol)]
The integrated value of the chemical shift value was taken by the ¹ H-NMR.
Integral value of δ 4.25 to 4.05 ppm = g
Integral value of δ 4.05 to 3.87 ppm = h
Integral value of δ 3.70 to 3.57 ppm = i
Integral value of δ3.41-3.30 ppm = j
Integral value of δ 1.15 to 1.12 ppm = k
The terminal derived from NPG is referred to as “NPG terminal”. Further, the NPG-derived structure part in the polycarbonate polyol other than the terminal is referred to as “in NPG”. Similarly, regarding 16HD, “16HD end” and “16HD medium” are set. Considering the number of each proton, calculate the number according to the following formula.
NPG end = j ÷ 2
In NPG = (h−j) ÷ 4
16HD end = i ÷ 2
16HD medium = (g-16HD end × 2-k ÷ 6 × 4) ÷ 4

<Quantitative analysis of ISB amount in polycarbonate diol by liquid chromatography (hereinafter sometimes abbreviated as “LC”)>
1 g of polycarbonate diol was precisely weighed into a 10 mL volumetric flask, and acetonitrile was added to make a constant volume of 10 mL. 100 μL of the solution was collected, 900 μL of pure water was added to precipitate polycarbonate diol, and the precipitated polycarbonate diol was removed by filtration. It measured by quantitative analysis by LC using the solution after filtration.

(Analysis conditions)
Column: Synergi 4 μm Hydro-RP 250 mmL × 4.6 mmI. D.
Injection volume: 50 μL
Eluent: 0.1% formic acid aqueous solution
Flow rate: 0.8mL / min
Column temperature: 40 ° C
Detector: RI

<Quantitative analysis of NPG content and neopentyl carbonate (NPC) content in polycarbonate diol by LC>
1 g of polycarbonate diol was precisely weighed into a 10 mL volumetric flask, and acetonitrile was added to make a constant volume of 10 mL. 100 μL of the solution was collected, 900 μL of pure water was added to precipitate polycarbonate diol, and the precipitated polycarbonate diol was removed by filtration. It measured by quantitative analysis by LC using the solution after filtration.

(Analysis conditions)
Column: CADENZA CD-C18 3 μm 250 mm × 4.6 mm I.D. D.
Injection volume: 50 μL
Eluent: Water / acetonitrile = 95/5 (volume ratio)
Flow rate: 0.8mL / min
Column temperature: 40 ° C
Detector: RI

<Quantitative analysis of diphenyl carbonate and phenol content in polycarbonate diol by LC>
1 g of polycarbonate diol was precisely weighed into a 10 mL volumetric flask, and acetonitrile was added to make a constant volume of 10 mL. The solution was used for quantitative analysis by LC.

(Analysis conditions)
Column: CAPCELL PAK 3 μm 75 mmL × 4.6 mmI. D. MG
Eluent: water / acetonitrile = 95 / 5-0 / 100 (volume ratio)
Flow rate: 1.0 mL / min
Column temperature: 40 ° C
Detector: UV

<APHA value>
In accordance with JIS K0071-1 (1998), the measurement was made in comparison with a standard solution placed in a colorimetric tube. As a reagent, a chromaticity standard solution of 1000 degrees (1 mg Pt / mL) (Kishida Chemical) was used. In addition, the solution was adjusted in steps of 5 until APHA50.

<Turbidity>
A 50% methylene chloride solution of polycarbonate diol was placed in a 10 mm cell using an integrating sphere turbidimeter PT-200 manufactured by Mitsubishi Chemical Corporation, and measurement was performed using a polystyrene calibration curve set in advance in the apparatus.

<Analysis of metal content>
After accurately weighing 0.1 g of polycarbonate diol and dissolving in 4 g of acetonitrile, 20 g of pure water was added to precipitate the polycarbonate diol, and the precipitated polycarbonate diol was removed by filtration. The filtered solution was diluted with pure water to a predetermined concentration, and the metal ion concentration was analyzed by ion chromatography. In addition, the metal ion concentration of acetonitrile used as a solvent was measured as a blank value, and the value obtained by subtracting the metal ion concentration of the solvent was used as the catalyst metal ion concentration of polycarbonate diol. Further, from the metal ion concentration analysis, a long-period periodic table group 1 element (excluding hydrogen) and a long-period periodic table group 2 element were extracted to yield a total molar concentration of the element. Measurement conditions are as shown in Table 1 below.

<Analysis of amount of phosphoric acid and phosphorous acid>
After precisely weighing 1 g of polycarbonate diol and dissolving in 10 mL of acetonitrile, pure water was added dropwise to adjust the volume to 100 mL, and the precipitated polycarbonate diol was removed by filtration. The phosphoric acid and phosphorous acid of the solution after filtration were analyzed by ion chromatography. In addition, the phosphoric acid and phosphorous acid density | concentration of acetonitrile used as a solvent were measured as a blank value, and the value which deducted the phosphoric acid and phosphorous acid density | concentration of a solvent part was made into the phosphoric acid and phosphorous acid density | concentration of polycarbonate diol. The measurement conditions are as shown in Table 2 below.

<Analysis of phosphorus atomic weight>
1 g of polycarbonate diol was precisely weighed, 10 mL of 89% sulfuric acid was added, and heating was performed from 200 ° C. to 400 ° C. on a high temperature hot plate. After cooling to room temperature, 1 mL of 69% nitric acid was added, and heating was again performed from 200 ° C. to 400 ° C. on a high temperature hot plate. The operation of adding nitric acid and heating was repeated until the decomposition solution became transparent. After cooling to room temperature, it was quantified with ICP-OES Vista-Pro (manufactured by Agilent) using the liquid obtained above, and the molar concentration of phosphorus atoms in the polycarbonate was calculated.

<Thin film distillation device>
An internal condenser having a diameter of 50 mm, a height of 200 mm, and an area of 0.0314 m 2 and a jacketed Shibata Kagaku Co., Ltd. molecular distillation apparatus MS-300 special type were used.

[Example 1]
In a 5 L glass separable flask equipped with a stirrer, distillate trap, and pressure regulator, 1,6-hexanediol (16HD): 404.3 g, isosorbide (ISB): 500.0 g, diphenyl carbonate: 1095.6 g Magnesium acetate tetrahydrate aqueous solution: 7.0 mL (concentration: 8.4 g / L, magnesium acetate tetrahydrate: 59 mg) and 0.0104 g of phosphorous acid were added, and then the 5 L glass separable flask was charged with The phase part was replaced with nitrogen gas. First, the internal temperature was raised to 160 ° C., and the contents were heated and dissolved. When the contents were dissolved, the pressure was reduced to 21 kPa in 5 minutes and reacted at 160 ° C. and 21 kPa for 150 minutes. Then, after the pressure was lowered to 0.40 kPa over 280 minutes, the reaction was carried out while distilling off phenol and unreacted dihydroxy compound while raising the temperature to 170 ° C. over 60 minutes. Magnesium acetate is a transesterification catalyst.

(Phosphorous acid added)
After confirming that the proportion of terminal groups derived from the carbonate compound out of all molecular chain terminals in the polycarbonate diol during the reaction was not detected by NMR, 0.0122 g of phosphorous acid was further added during the reaction. Polycarbonate diol was obtained by adding to polycarbonate diol. The reaction results are shown in Table 3.

[Comparative Example 1]
This was carried out in the same manner as in Example 1 except that phosphorous acid was not put into a 5 L glass separable flask and phosphorous acid was not added to the polycarbonate diol during the reaction. The results are shown in Table 3.

[Comparative Example 2]
The same operation as in Example 1 was carried out except that the amount of phosphorous acid placed in the 5 L glass separable flask was changed from 0.0104 g to 0.0207 g.
However, the reaction was carried out at 160 ° C. and 21 kPa for 150 minutes, but since the distillation of phenol could not be confirmed, the reaction was terminated during the reaction.

[Comparative Example 3]
This was carried out in the same manner as in Example 1 except that the magnesium acetate tetrahydrate aqueous solution was not put into a 5 L glass separable flask and the amount of phosphorous acid was changed from 0.0104 g to 0.2075 g.
However, although the reaction was carried out at 160 ° C. and 21 kPa for 180 minutes, the reaction was terminated in the middle of the reaction because the distillation of phenol could not be confirmed.

[Example 2]
A 3 L glass separable flask equipped with a stirrer, a distillate trap, and a pressure control device is charged with 33.4 L of neopentyl glycol (NPG): 343.4 g, diphenyl carbonate: 1046.8 g, and 85 wt% phosphoric acid 0.0013 g. The gas phase portion of the glass separable flask was replaced with nitrogen gas. The internal temperature was raised to 140 ° C. and then heated at 140 ° C. for 20 hours.
Thereafter, 1,6-hexanediol (16HD): 259.8 g, magnesium acetate tetrahydrate aqueous solution: 2.8 mL (concentration: 8.4 g / L, magnesium acetate tetrahydrate: 24 mg) was added to 3 L glass separa. Additional addition was made to the bull flask, and the gas phase part of the 3 L glass separable flask was replaced with nitrogen gas. Next, the internal temperature was raised to 160 ° C., and the contents were heated and dissolved. When the contents were dissolved, the pressure was reduced to 20 kPa in 5 minutes and reacted at 160 ° C. and 20 kPa for 20 minutes. Then, after reducing the pressure to 1.3 kPa over 340 minutes, the reaction was conducted while distilling off and removing phenol and unreacted dihydroxy compound at 160 ° C. for 60 minutes.

(Phosphoric acid added)
After confirming that the ratio of the terminal groups derived from the carbonate compound among all the molecular chain terminals in the polycarbonate diol during the reaction was not detected by NMR, 0.0091 g of 85 wt% phosphoric acid was added during the reaction. Polycarbonate diol was obtained by adding to polycarbonate diol. The reaction results are shown in Table 3.

[Comparative Example 4]
The same procedure as in Example 2 was carried out except that the charging weight described in Table 3 was changed and phosphoric acid was not added to the 3 L glass separable flask, and no phosphoric acid was added to the polycarbonate diol during the reaction. did. The results are shown in Table 3.

Comparison between Example 1 and Comparative Example 1 shows that when an appropriate amount of phosphorous acid is added and the ester exchange reaction is carried out, a polycarbonate diol having a low APHA value and good color tone can be produced without reducing the reaction rate.
In Comparative Example 2, it can be seen that since the amount of phosphorous acid added is larger than the amount of catalyst, the catalyst is deactivated and the reaction rate becomes slow, and the reaction cannot be performed substantially.
In Comparative Example 3, an attempt was made to perform polymerization only by adding phosphorous acid without adding a metal catalyst.
Moreover, it is understood from the comparison between Example 2 and Comparative Example 4 that when an appropriate amount of phosphorous acid is added and the ester exchange reaction is performed, the effect of improving the color tone becomes more remarkable when the addition of the ester exchange catalyst is delayed.
As above-mentioned, it turns out that the color tone of the polycarbonate diol to produce | generate is improved by performing transesterification by adding a suitable quantity phosphoric acid or phosphorous acid.

[Example 3]
The polycarbonate diol obtained in Example 1 was subjected to thin film distillation (jacket oil temperature: 180 ° C., pressure: 0.027 kPa) at a flow rate of 20 g / min. The results are shown in Table 4.

[Comparative Example 5]
The polycarbonate diol product obtained in Comparative Example 2 was subjected to thin film distillation (jacket oil temperature: 180 ° C., pressure: 0.027 kPa) at a flow rate of 20 g / min. The results are shown in Table 4.

  From the results in Table 4, the polycarbonate diol containing an appropriate amount of phosphorous acid can suppress the increase in molecular weight and coloration in a heating state such as thin film distillation, and the amount of residual monomer can be suppressed as compared with the case where the polycarbonate diol is not contained. Since it can reduce, it is useful.

  According to the method for producing a polycarbonate diol of the present invention, the coloring of the polycarbonate diol can be suppressed in the raw material preparation, the transesterification reaction, and the purification step, and further, the polycarbonate diol having excellent thermal stability can be obtained. Therefore, for example, when a polyurethane is produced using a polycarbonate produced by the production method, there is little possibility that the color tone or each physical property of the polyurethane is changed, and this is extremely useful industrially.

Claims (8)

A method for producing a polycarbonate diol having a number average molecular weight of 250 or more and 5500 or less by subjecting a dihydroxy compound and a carbonate compound to an ester exchange reaction using an ester exchange catalyst.
The transesterification reaction is performed in the presence of phosphoric acid and / or phosphorous acid, and the total amount of phosphoric acid and phosphorous acid is 0.05 mol times or more and 0.9 mol times or less with respect to 1 mol of the transesterification catalyst. A process for producing a polycarbonate diol, characterized in that   The transesterification catalyst is a compound of at least one element selected from the group consisting of long-period periodic table group 1 elements (excluding hydrogen) and long-period periodic table group 2 elements. The manufacturing method of the polycarbonate diol of Claim 1.   The method for producing a polycarbonate diol according to claim 1 or 2, wherein the ester exchange catalyst is added to a mixture of the dihydroxy compound, the carbonate compound, and phosphoric acid and / or phosphoric acid, and the ester exchange reaction is performed.   The method for producing a polycarbonate diol according to any one of claims 1 to 3, wherein the amount of the transesterification catalyst is 1 µmol to 200 µmol with respect to 1 mol of the dihydroxy compound.   The method for producing a polycarbonate diol according to any one of claims 1 to 4, wherein the carbonate compound is diaryl carbonate.   With the progress of the transesterification reaction, the ratio of the terminal group derived from the carbonate compound out of the total molecular chain terminals of the polycarbonate diol becomes 10 mol% or less, and then the polycarbonate diol is further added with phosphoric acid and / or phosphorous acid. The method for producing a polycarbonate diol according to any one of claims 1 to 5, further comprising a purification step.   A polycarbonate diol produced by the method for producing a polycarbonate diol according to any one of claims 1 to 6, wherein the turbidity measured with an integrating sphere turbidimeter is 2.0 ppm or less. Polycarbonate diol.   It is the polycarbonate diol manufactured by the manufacturing method of the polycarbonate diol of any one of Claims 1 thru | or 6, Comprising: The Hazen color number measured based on JISK0071-1 (1998) is 60 or less. A polycarbonate diol characterized by that.