JPH10316765A - Thermoplastic resin pellet and polyester molding prepared therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain thermoplastic resin pellets which forms a reduced amt. of a cyclic oligomer when molten by using a thermoplastic resin containing a phosphoric-acid-derived-hydroxyl-containing P compound selected among a phosphoric acid comprising a P atom having a specified oxidation number, a phosphate or a phosphoric ester. SOLUTION: 2-10 wt.% phosphoric-acid-derived hydroxylcontaining P compound selected among a phosphoric acid, a phosphate and a phosphoric ester is added to a thermoplastic resin having an intrinsic viscosity of 0.5-2.0, and the mixture is melt-kneaded to prepare master pellets. Next, the master pellets are mixed with a thermoplastic pellets in a specified ratio, and the mixture is extruded at 250-270 deg.C and stretched at a draw ratio of 1.5-3.5 and a temperature of 80-110 deg.C to obtain a molding. The phosphorus compound comprises a P atom with an oxidation number of V and is a compound selected among orthophosphoric acid, metaphosphoric acid, polymetaphosphoric acid, polyphosphoric acid and salts and esters thereof and has phosphoric-acid-derived hydroxyl groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin pellet containing a specific phosphorus compound and a polyester molded article using the same. More specifically, when producing a polyester resin molded product, by using the above-mentioned thermoplastic resin pellets mixed with the raw material pellets, it is possible to suppress the generation of a cyclic oligomer of a unique polyester during the production of the polyester molded product. The present invention relates to a thermoplastic resin pellet for a master pellet.

[0002]

2. Description of the Related Art Polyethylene terephthalate or a polyester mainly composed of polyethylene terephthalate (hereinafter referred to as "PET polyester") is excellent in mechanical strength, heat resistance, transparency, gas barrier properties, etc., and is light and inexpensive. , Bottles, sheets, films, fibers, foams and the like. In particular, it is suitable as a filling container for foods and drinks such as carbonated drinks, fruit drinks, liquid seasonings, edible oils, alcohol, wine and the like.

[0003] Such a PET polyester is mainly produced by subjecting a terephthalic acid component and an ethylene glycol component to main components, esterifying them, and then performing melt polycondensation in the presence of a polycondensation catalyst, and further performing solid phase polymerization. Is done.

[0004] The pellets of the PET polyester thus produced contain a considerable amount of cyclic oligomers (cyclic dimer to cyclic 10-mer of ethylene terephthalate). Volume reductions have been made. However, it is known that even if cyclic oligomers are reduced by solid-phase polymerization, they are regenerated when melt extrusion is performed at the time of molding processing, which is an obstacle to the production process of PET-based polyester products. For example, when manufacturing a hollow container such as a bottle, since cyclic oligomers are regenerated during injection molding, mold contamination occurs, or these cyclic oligomers are mixed as foreign substances in polyester, resulting in quality deterioration. There was a problem. In addition, during the melt spinning, the cyclic oligomer accumulates around the discharge hole of the nozzle, and eventually the yarn is deformed around the discharge hole, or the yarn breaks or the yarn becomes uneven. Furthermore, when a film is produced, the cyclic oligomer is regenerated when the pellets are melted, so that there is a problem that the film is cut or the quality is reduced.

[0005] Therefore, in order to solve the above-mentioned problems concerning the cyclic oligomer, not only the content of the cyclic oligomer is reduced by solid-phase polymerization, but also the production of the cyclic oligomer upon remelting is suppressed and the content is not increased. You need to do that.

Therefore, various methods have been hitherto attempted to solve these problems. For example, Japanese Unexamined Patent Publication
Japanese Patent No. 322082 proposes a method of copolymerizing a PET-based polyester with a monofunctional component having a hydroxyl group or a carboxyl group. However, in this method, the terminal functional group is blocked by a monofunctional component at the time of melt polycondensation, so that the polycondensation reaction is inhibited, and there is a problem that a polyester having a large intrinsic viscosity cannot be obtained.

Further, in producing a PET polyester through a melt polycondensation step and a solid phase polymerization step, hot water or steam treatment is performed after the solid phase polymerization step to remove a polycondensation catalyst contained in the PET polyester. Methods for suppressing the generation of cyclic oligomers during melt molding by deactivation (JP-A-3-174441, JP-B-7-37515, JP-A-8-283393, etc.) have been proposed. However, these methods require a hot water treatment device or a steam treatment device in addition to the polymerization device in order to deactivate the polycondensation catalyst, and there is a problem that the cost is increased.

Further, Japanese Patent Application Laid-Open No. 8-283393 discloses a method in which a metal derived from a polycondensation catalyst and other specific metal atoms are added in an esterification step or a melt polycondensation step to suppress the formation of cyclic oligomers. However, in this method, since a metal atom other than the polycondensation catalyst atom is added, the polycondensation reaction of the PET-based polyester is inhibited in a step after the addition of the metal atom, and the polycondensation rate is reduced. There was a problem that it would.

[0009]

SUMMARY OF THE INVENTION The present invention proposes a thermoplastic resin pellet capable of reducing the amount of cyclic oligomer produced during melt molding and a PET-based polyester molded article using the same.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have made it possible to use thermoplastic resin pellets containing a specific phosphorus compound as master pellets.
The inventors have found that the above problems can be solved, and have reached the present invention.

That is, the gist of the present invention is as follows. (1) Thermoplastic resin pellets containing a phosphorus compound comprising a phosphorus atom having an oxidation number (V). However, phosphorus compounds composed of phosphorus atoms having an oxidation number (V) include orthophosphoric acid, metaphosphoric acid,
1 selected from the group consisting of polymetaphosphoric acid represented by (HPO ₃ ) _m (m is an integer of 3 or more) and polyphosphoric acid represented by H _{n + 2} P _n O _{3n + 1} (n is an integer of 2 or more) At least one kind of phosphoric acid or a salt or ester thereof, and these phosphorus compounds have a hydroxyl group derived from phosphoric acid. (2) A polyester molded article comprising the polyester produced through the melt polymerization step and the solid phase polymerization step and the thermoplastic resin pellets according to the above (1).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Oxidation number in the thermoplastic resin pellet of the present invention
Examples of the phosphorus compound comprising a phosphorus atom of (V) include orthophosphoric acid, metaphosphoric acid, polymetaphosphoric acid represented by (HPO ₃ ) _m (m is an integer of 3 or more), H _{n + 2} P _n O _{3n + 1} ( and n is an integer of 2 or more), or a salt or ester thereof. These phosphorus compounds need to have a hydroxyl group derived from phosphoric acid. Here, the hydroxyl group derived from phosphoric acid means a hydroxyl group bonded to a phosphorus atom having an oxidation number (V). Specifically, there are orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, monoaluminum phosphate, magnesium monohydrogen phosphate, monoethyl ester phosphate, monooctyl phosphate, and the like. Particularly preferred are aluminum aluminum acid, monoethyl phosphate and pyrophosphoric acid.

At this time, it is necessary that the compounding amount of the phosphorus compound comprising a phosphorus atom having an oxidation number (V) is in the range of 2 to 10% by weight based on the thermoplastic resin. If the amount is less than 2% by weight, the mixing efficiency at the time of melt-kneading with the raw material pellets tends to decrease. If the amount exceeds 10% by weight, there are problems such as a decrease in viscosity and coloring of the thermoplastic resin.

The thermoplastic resin in the present invention includes PET polyester, polybutadiene, butadiene / styrene copolymer, acrylic rubber, ethylene / propylene copolymer, ethylene / propylene / butadiene copolymer, natural rubber, chlorinated butyl rubber, Elastomers such as chlorinated polyethylene and their acid-modified products such as maleic anhydride, styrene / maleic anhydride copolymer, styrene / phenylmaleimide copolymer, polyethylene, polypropylene, butadiene / acrylonitrile copolymer, polyvinyl chloride, polyvinyl chloride Butylene terephthalate, polyacetal, polyvinylidene fluoride, polysulfone, polyphenylene sulfide, polyether sulfone, phenoxy resin, polyphenylene ether, polymethyl methacrylate, polyether ketone Emissions, polycarbonate, polytetrafluoroethylene, polyarylate, and polyimide, and the like, PET-based polyester is particularly preferable.

The PET polyester is mainly composed of a terephthalic acid component and an ethylene glycol component. In addition to these components, phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalene Aromatic dicarboxylic acid components such as dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, diphenylsulfodicarboxylic acid,
Aromatic polycarboxylic acid components such as trimellitic acid, pyromellitic acid and their anhydrides, oxalic acid, succinic acid,
Aliphatic dicarboxylic acid components such as adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,
Aliphatic diol components such as 3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, 1,5-pentanediol, neopentyl glycol, triethylene glycol, and polyethylene glycol;
Aliphatic polyhydric alcohol components such as trimethylolpropane and pentaerythritol; alicyclic diol components such as 1,4-cyclohexanedimethanol and 1,4-cyclohexanediethanol; aromatics such as ethylene oxide adducts of bisphenol A and bisphenol S A copolymer component such as a diol component, a hydroxycarboxylic acid component such as 4-hydroxybenzoic acid, and ε-caprolactone may be contained in a range that does not impair the properties of PET (usually within 20 mol%).

The intrinsic viscosity of the above thermoplastic resin is not particularly limited as long as it can be melt-kneaded with a phosphorus compound to form a resin pellet for a master pellet, but is usually in the range of 0.5 to 2.0. Is used.
When a PET-based polyester is used as the thermoplastic resin, one having an intrinsic viscosity in the range of 0.5 to 1.5 is usually used.

Next, a PET-based polyester molded article, particularly a PET-based hollow container, using the thermoplastic resin pellet of the present invention will be described.

In order to produce the above-mentioned molded article, first, the thermoplastic resin pellet of the present invention is melt-kneaded with PET-based polyester as a raw material pellet, and then a hollow container is obtained. At this time, the mixing ratio of the thermoplastic resin pellets to the PET polyester is preferably in the range of 1/1000 to 1/1, more preferably in the range of 1/100 to 1/10.

The method of manufacturing the hollow container is based on the conventional PET.
The method used in the stretch blow molding method used in the system polyester can be used as it is. For example, a preform is formed by injection molding using the above-described melt-kneaded material, and then a preform is formed by a hot parison method of biaxial stretch blow molding or injection molding, and the preform is preheated, and then biaxially molded. A cold parison method of stretching blow molding or the like can be employed. At this time, the temperature of each part of the cylinder and the nozzle of the molding machine is usually from 250 to 290 ° C. The stretching temperature is usually 70
To 180 ° C., preferably 80 to 110 ° C., and the stretching ratio is 1.5 to 3.5 times, preferably 2 to 3 times in the stretching direction.

The obtained hollow container can be used as it is, but especially when it is necessary to heat-fill the content liquid, the same blow molding mold used for molding or a mold provided separately. It can be used after heat setting in it to improve heat resistance.

[0021]

The reason why the formation of cyclic oligomers in the polyester of the present invention during melting is suppressed is that the phosphorus compound comprising a phosphorus atom having an oxidation number (v) coordinates (interacts) with the polyester polycondensation catalyst. In order to stabilize the polyester, it is assumed that the formation of cyclic oligomers is suppressed when the polyester is melted at a high temperature.

[0022]

Next, the present invention will be described specifically with reference to examples. The raw materials and measuring methods used in the examples and comparative examples are as follows. 1. Ingredients ・ PET: manufactured by Unitika ・ Daiichi aluminum phosphate: manufactured by Ishizu Pharmaceutical ・ Monoethyl phosphate: manufactured by Johoku Chemical Co., Ltd. ・ Pyrophosphate: manufactured by Sigma-Aldrich Japan

2. Measurement Method (a) Intrinsic Viscosity [η] Measured at a temperature of 20 ° C. using an equal mixture of phenol and ethane tetrachloride as a solvent, and expressed in units of dl / g. (b) Cyclic oligomer content After dissolving a part of the hollow container in a mixed solvent of hexafluoroisopropanol / chloroform (1/1, volume ratio), the solution was poured into acetonitrile to precipitate a polymer,
The cyclic oligomer (cyclic dimer to cyclic 10-mer of ethylene terephthalate) in the filtrate filtered through the membrane filter was subjected to high performance liquid chromatography (Waters, 60
(0E liquid delivery system and 486 detector).

Example 1 PET resin pellets containing 2% by weight of aluminum monophosphate (hereinafter referred to as "master pellets") based on PET ([η] = 0.85) and PET ([η] = 0.77)
Hereinafter, it is referred to as “raw material pellet”. ) Were mixed at a weight ratio of 5/95 to form a hollow container. That is, using the above-mentioned mixture, each part of the cylinder and the nozzle temperature 280 ° C.,
Screw rotation speed 100 rpm, injection time 10 seconds, cooling time 10
The preform was molded using an injection molding machine (model ASB-50HT, manufactured by Nissei ASB Co.) set at a mold temperature of 15 ° C. for seconds. Next, the preform is stretch blow-molded at 100 ° C. in an atmosphere at a blow pressure of 2 MPa to obtain an average body thickness of 300 mm.
A hollow container having a volume of 1 μm and an inner volume of 1 liter was prepared, subjected to compression and tension treatment, and then heat-set in a mold set at 110 ° C. for 10 seconds. Although 2,000 hollow containers were continuously molded under the above conditions, no mold contamination was observed in any of injection molding, stretch blow molding, and heat setting. Further, the amount of the cyclic oligomer in the obtained hollow container was quantified by using high performance liquid chromatography (HPLC).

Examples 2 to 5 The compounds shown in Table 1 were used in place of monoaluminum phosphate, and the phosphorus compound content in the master pellets and the ratio between the master pellets and the raw material pellets were changed as shown in Table 1. Other than the above, 2,000 hollow containers were continuously formed in the same manner as in Example 1, but no mold contamination was observed in any case. Moreover, the cyclic oligomer content of the hollow container was quantified using HPLC.

Comparative Example 1 Using only raw material pellets (PET), 2,000 hollow containers were continuously molded in the same manner as in Example 1, and mold contamination was observed. Moreover, the cyclic oligomer content of the hollow container was quantified using HPLC.

Table 1 summarizes the results of Examples 1 to 5 and Comparative Example 1.

[0028]

[Table 1]

[0029]

According to the present invention, it is possible to obtain a high-quality polyester molded article with a small amount of cyclic oligomer produced during melt molding.

Claims (5)

[Claims] 1. A thermoplastic resin pellet containing a phosphorus compound comprising a phosphorus atom having an oxidation number (V). However, phosphorus compounds composed of a phosphorus atom having an oxidation number (V) include orthophosphoric acid, metaphosphoric acid, polymetaphosphoric acid represented by (HPO ₃ ) _m (m is an integer of 3 or more), and H _{n + 2} P _n O _{3n + 1} (n is an integer of 2 or more) one or more phosphoric acids selected from the group consisting of polyphosphoric acids, or salts or esters thereof,
These phosphorus compounds have a hydroxyl group derived from phosphoric acid. 2. The thermoplastic resin pellet according to claim 1, wherein the thermoplastic resin is polyethylene terephthalate or a polyester mainly composed of polyethylene terephthalate. 3. The thermoplastic resin pellet according to claim 1, wherein the content of the phosphorus compound is 2 to 10% by weight. 4. A polyester molded article comprising polyethylene terephthalate produced through a melt polymerization step and a solid phase polymerization step or a polyester mainly comprising the same, and the thermoplastic resin pellets according to claim 1. 5. The polyester molded article according to claim 4, wherein the molded article is a hollow container.