JPH0131765B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to providing a resin that can be molded into an adhesive, a binder, a coating, an emulsifier, a film or a fiber, and at the same time provides excellent water resistance. Polyvinyl alcohol (hereinafter abbreviated as PVA) has long been known as a typical water-soluble polymer, and is used as a raw material for synthetic fibers such as vinylon or film, and for a wide range of industrial applications such as adhesives, binders, coatings, and emulsifiers. has been used.
In these applications, it is often necessary to improve water resistance, and many methods for improving water resistance have been proposed. Regarding technologies related to water resistance and insolubilization, see "Povaal" (revised new edition) by Nagano, Yamane, and Toyoshima, Kobunshi Publishing Association (1981).
Reviewed on pages 256-261. Formalin, acetaldehyde, etc. are used to make vinylon water resistant, but they have not been put into practical use when used as other glues or emulsifiers due to problems such as odor. Dialdehyde compounds such as glyoxal and glutaraldehyde, and polyvalent aldehyde compounds such as dialldehyde starch are known as water-resistant agents for PVA, but in order to create a film that can withstand boiling water, the amount used must be high. It also has the disadvantage of being easily colored during heat treatment. N-methylol urea and N-methylol melamine also have water resistance properties, but have the disadvantage of emitting a formalin odor. Compounds containing inorganic elements such as boron, titanium, zircon, chromium, and silicon also have crosslinking properties.
It is used for water resistance, but in many cases, when these substances are added to a PVA aqueous solution, thickening or gelation occurs, or the viscosity of the liquid becomes unstable. There are few examples of it being used. In contrast to water resistance using the above additives,
There are also a few known proposals to modify PVA itself to make it water resistant. The saponified copolymer of arylidene diacetate and vinyl acetate is a modified PVA with aldehyde in the side chain, and is easily crosslinked by acid treatment. However, if the amount of modification is increased in order to provide sufficient water resistance, cross-linked insoluble matter tends to occur during the production of PVA, and it tends to be easily colored, so it has not yet been put to practical use. Thus, it has been more difficult than expected to industrially and effectively impart water resistance or crosslinking properties to PVA, and a sufficiently effective method has not yet been known. Based on this situation, the inventors of the present invention
As a result of our research, we aimed to establish a method to industrially produce PVA at low cost by introducing a crosslinkable group that gives PVA itself water resistance, and which has excellent solubility in solvents such as water before crosslinking. formula in the molecule (Here, R ¹ is a hydrogen atom or a lower alkyl group,
R ² each represents a hydrogen atom or an alkyl group. ) Modification containing copolymerized units shown in
The present invention was completed by discovering that a resin with extremely high water resistance can be obtained by removing the solvent from a PVA solution, especially an aqueous solution, under acidic conditions or under conditions that generate acidic substances during drying. Modifications used as starting materials in the present invention
PVA itself is a novel compound that was previously unknown. This modified PVA is a combination of vinyl esters, especially vinyl acetate, with the formula CH ₂ = CR ¹ −CONHCH ₂ O−R ²
(R ¹ is a hydrogen atom or a lower alkyl group, R ² is a hydrogen atom or an alkyl group) N-alkoxymethyl group-containing monomer, in particular, R ¹ is a hydrogen atom or a methyl group, and R ² has 1 to 1 carbon atoms. N-alkoxymethyl (meth)acrylamide, particularly preferably N-methoxymethylacrylamide or N-n-butoxymethylacrylamide, which is the alkyl group of No. 4, is copolymerized using a radical polymerization initiator, and then this copolymer is The copolymer is produced by applying an alkali catalyst to an alcohol solution to partially or highly saponify the vinyl ester units in the copolymer into vinyl alcohol units. Vinyl esters that can be used to produce this modified PVA can be copolymerized and then saponified to become vinyl alcohol, so any vinyl ester can have essentially the same effect, but usually vinyl acetate, formic acid, etc. Examples include vinyl, vinyl propionate, and vinyl acetate is more preferable from an economic standpoint. In addition, R ¹ in the alkoxymethyl group-containing monomer represented by CH ₂ = CR ¹ −CONHCH ₂ O−R ²
is a hydrogen atom or a lower alkyl group, but usually a hydrogen atom or a methyl group is preferred, and R ² can be a hydrogen atom or an alkyl group of any chain length in terms of imparting crosslinking properties, but usually Particularly preferred are alkyl groups having 1 to 4 carbon atoms. Specific examples of this monomer include N-methylolacrylamide, N-methylolmethacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-ethoxymethylacrylamide, N-ethoxymethylmethacrylamide, N-n- Propoxymethylacrylamide, N-n-propoxymethylmethacrylamide, N-isopropoxymethylacrylamide, N-isopropoxymethylmethacrylamide, N-n-butoxymethylacrylamide, N
-n-butoxymethylmethacrylamide, N-isobutoxymethylacrylamide, N-isobutoxymethylmethacrylamide, N-tert-butoxymethylacrylamide, and N-tert-butoxymethylmethacrylamide, among which N-
Methoxymethylacrylamide or N-n-
Butoxymethylacrylamide is particularly preferred in terms of effectiveness and economy. These monomers are well known in the art; for example, British Patent No. 955420 describes copolymers with vinyl acetate and acrylic esters. However, N
- There is no known copolymer produced by saponifying a copolymer of alkoxymethyl (meth)acrylamide and vinyl ester.
It is completely unknown that a resin with excellent industrially important performance as shown in the present invention can be derived. Copolymerization of the above-mentioned N-alkoxymethyl (meth)acrylamides and vinyl esters can be carried out using any polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization, but many of the methods of the present invention Solution polymerization is usually preferred for this purpose. As the solvent used in solution polymerization, lower alcohols, particularly methanol, are industrially suitable. Bulk polymerization and solution polymerization can be carried out either batchwise or continuously, while suspension polymerization and emulsion polymerization are usually carried out batchwise. In the case of a batch method, it is well known that the monomer composition changes with the polymerization rate according to the comonomer reactivity ratio (r ₁ , r ₂ ), but when the monomer composition is constant, In order to obtain a copolymer having a uniform copolymer composition, it is desirable to adopt a so-called semi-batch method in which one or both monomers are added so that the following is achieved. In this case, RJHanna is one of the methods for calculating the amount added.
Engineering Chemistry, Vol.49, No.2, 208―
209 (1957). In the case of continuous multi-column copolymerization, for the same reason, it is desirable to add monomers to the second and subsequent columns so that the monomer composition in each column is constant. As a polymerization initiator, 2,2'-azobisisobutyronitrile,
1,1'-azobis-(cyclohexane-1-carbonitrile), 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobis-
(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis-(2-amidinopropane) dihydrochloride, benzoyl peroxide, potassium persulfate, ammonium persulfate, t-butyl hydroperoxide, peroxide Known radical polymerization initiators such as di-t-butylcumene hydroperoxide may be used. Further, a degree of polymerization regulator such as acetaldehyde or alkyl mercaptan can also be added to the polymerization system. The polymerization reaction temperature is usually selected from the range of 50°C to the boiling point. Monomer reaction rate is determined by economic efficiency,
It can be determined as appropriate depending on the purpose, such as adjusting the degree of polymerization.
The amount of N-alkoxymethylacrylamide units in the copolymer is appropriately selected depending on the application and is not particularly limited, and a copolymer with any composition can be synthesized.
It is preferably selected from the range of 0.05 to 10 mol%. Further, in the case of solution polymerization, the degree of polymerization of the copolymer can be adjusted by adjusting the amount of the solvent, especially methanol, and the amount of aldehydes. There are no restrictions on the degree of polymerization,
Copolymers with a wide range of polymerization degrees can be synthesized, but the degree of polymerization of the saponified product described later is usually selected from the range of 200 to 3,600. After the copolymerization is completed, if vinyl ester remains in the reaction solution, it is necessary to separate and remove it by distillation or the like. When the N-alkoxymethyl (meth)acrylamide monomer remains, it may be removed, or it may be allowed to remain without any problem in many cases. In addition to vinyl ester and N-alkoxymethylacrylamide, other unsaturated monomers copolymerizable with these monomers, such as ethylene, propylene, α-hexene, α-octene, etc., may be used in carrying out such polymerization. α-olefins such as (meth)acrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid, etc., or their alkyl esters or alkali salts thereof; (meth)acrylamide, N-methylolacrylamide, etc. unsaturated amides; sulfonic group-containing monomers such as 2-acrylamide-2-methylpropanesulfonic acid or its salts; N-(2-dimethylaminoethyl)acrylamide, N-(3-dimethylaminopropyl)methacrylamide, N-(1,1-dimethyl-3-dimethylaminopropylacrylamide)
or cationic group-containing monomers such as their quaternary compounds; alkyl vinyl ethers; styrene;
Unsaturated imidazole compounds such as N-vinylimidazole, N-vinyl-2-methylimidazole or their quaternary compounds; N-vinylacetamide, N-vinyl-N-methyl-acetamide, N
-vinyl-N-methylformamide, methyl-N
-vinyl carbamate, ethyl-N-vinyl carbamate, tert-butyl-N-vinyl carbamate, methyl-N-isopropenyl carbamate,
Ethyl-N-isopropenyl carbamate, tert
-Produced by polymerizing in the coexistence of N-vinyl or N-isopropenyl compounds such as butyl-N-isopropenyl carbamate so that these monomer units are present in the copolymer at about 10 mol% or less. You can also do that. The vinyl ester moiety of the copolymer thus obtained is then saponified by a saponification reaction as shown below. It is usually advantageous to carry out the saponification reaction as a solution of the copolymer in alcohol, especially methanol. Not only anhydrous alcohols but also those containing a small amount of water can be used depending on the purpose, and organic solvents such as methyl acetate and ethyl acetate may be optionally contained. As saponification catalysts, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, sodium methylate,
Alcoholates such as potassium methylate or alkaline catalysts such as ammonia, or acidic catalysts such as hydrochloric acid or sulfuric acid may be used. In the process of studying the present invention, it became clear that when acidic catalysts are used, they tend to be cross-linked and become unnecessary when drying the saponification reaction product.For this reason, industrially, alkaline catalysts, especially from the economic point of view, are Sodium oxide is most suitable for the purposes of this invention. The saponification temperature is usually 10
Selected from the range of ~50℃. It is undesirable to leave the product under strong alkaline or acidic conditions at a high temperature of 100°C or higher for a long time, as the bond between the amide group or alkoxymethyl group will gradually decompose, but it is usually not necessary to leave it under such conditions. During saponification, the amide bond or alkoxymethyl group remains stable without being substantially decomposed. Through the saponification reaction, the vinyl ester units are partially or highly saponified and converted into vinyl alcohol units, but this conversion rate can be set to any value depending on the intended use of the resin of the present invention. , for normal purposes the vinyl alcohol units in the copolymer are 99.95
It is preferable that the content of the vinyl ester unit is 0 to 2.9 mol%. Further, the content of N-alkoxymethyl (meth)acrylamide units is usually preferably in the range of 0.05 to 10 mol%, as described above. As the chain length of the alkyl group of the N-alkoxymethyl (meth)acrylamides used increases, the water solubility of the resulting modified PVA may decrease when the degree of modification is high and/or when the content of vinyl acetate units is high. Yes, water-soluble modified PVA
If this is the purpose, it is necessary to adjust the type and content of N-alkoxymethyl (meth)acrylamides and the content of vinyl acetate units. It is industrially preferable to use a method in which a white gel or precipitate is produced as the saponification reaction progresses, as in the case of ordinary PVA, and this can be crushed or precipitated as necessary.
A modified PVA copolymer powder can be obtained by washing and drying. As long as drying is carried out for the purpose of evaporating the solvent, it will not affect the solubility of the resulting PVA, but care must be taken since drying will become partially cross-linked and insolubilized if it is left at high temperatures of 100°C or higher for a long time. There is no need to put it under any conditions.
The modified PVA copolymer used in the present invention is a general PVA copolymer.
Similarly, many copolymers whose compositions have been adjusted to make them water-soluble can be stored and transported in powder form. liquid can be obtained. When the content of N-alkoxymethylacrylamide units is high and/or when the content of vinyl ester units is high and water solubility is low, use a mixed solvent of alcohols such as methanol, ethanol, propanol, butanol and water, or dimethyl Sulfoxide can also be used as a solvent. At first glance, the modified PVA copolymer used in the present invention is PVA.
Although it is similar to PVA, it can be easily distinguished from other PVA by its distinctive property of providing a film strength that can withstand boiling water when cured under appropriate conditions. Curing conditions include denatured PVA solution, especially mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, organic acids such as acetic acid, oxalic acid, citric acid, and tartaric acid, and acid salts such as aluminum sulfate, ammonium nitrate, ammonium sulfate, and ammonium chloride in an aqueous solution. Another method is to use a catalytic amount of salts that produce acidic substances during drying, and to dry by heating. The degree of crosslinking and water resistance may vary depending on the purpose, and can be adjusted by selecting the amount of catalyst, heating temperature, and heating time. In order to provide a film that can withstand boiling water, the pH of the solution should be 1 to 5 for modified PVA copolymers containing 0.1 to 10 mol% of N-alkoxymethyl (meth)acrylamide units.
As an example, a heating temperature range of 60 to 160°C and a heating time range of 30 seconds to 30 minutes can be cited. In this way, the resin with excellent water resistance obtained by the present invention can be used in various applications that take advantage of the crosslinking water resistance function in addition to the performance possessed by PVA. For example, sizing agents for fibers, fiber processing agents, surface sizing agents for paper, binders for pigment coating, internal additives for paper making,
Improving agents for amino resin adhesives, emulsion stabilizers for emulsion polymerization, wall materials for microcapsules, inorganic binders such as gypsum board, glass fiber, rock wool, and ceramics, photosensitive resins, stabilizers for suspension polymerization, films, Its applications are wide-ranging, including molded products such as sheets, pipes, tubes, and fibers, adhesives for wood, paper, aluminum foil, and plastics, binders for nonwoven fabrics, cement and mortar additives, and selective separation membranes. This is of great significance. Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, parts or % below mean parts by weight or % by weight unless otherwise specified. Example 1 8.8 N-methoxymethylacrylamide units
The N-methoxymethylacrylamide-vinyl acetate copolymer containing mol% is saponified to yield 8.8 mol% N-methoxymethylacrylamide units, 88.4 mol% vinyl alcohol units, and vinyl acetate units.
Modified PVA with a polymerization degree of 2200 at 2.8 mol% was obtained.
(Modified PVA No. 1) Phosphoric acid was added to a 9% aqueous solution of this modified PVA to adjust the pH to 1.6, and the film was formed at 75° C. for 1 hour to form a film with a thickness of approximately 50 μm.
This film was insoluble in cold or boiled water. Example 2 Add 1N to a 9% aqueous solution of modified PVA shown in Table 1.
After adding and mixing a predetermined amount of sulfuric acid aqueous solution and measuring the pH at 20°C, film formation was performed at 75°C for 1 hour and denatured.
A PVA film with a thickness of about 50μ was created. Measure the weight of this film sample (100 mm x 100 mm) either as it is or after heat-treating it in a hot air dryer for a specified period of time. If the film maintains its shape, take it out and measure its weight after it is completely dry. The elution loss of the film due to boiling water was determined. The results are shown in Table 2. For comparison, film formation was performed without adding sulfuric acid to an aqueous solution of modified PVA No. 4 (Comparative Example 1), and unmodified PVA (saponification degree 98.5).
Table 2 also shows the case where similar table values were calculated using mol% and degree of polymerization (1780).

【table】

【table】

[Table] Example 3 2 parts of ammonium chloride powder was added and mixed to 100 parts of a 9% aqueous solution of modified PVA Nos. 3 and 6, and film formation was carried out in the same manner as in Example 2 at 75°C for 1 hour. , a film with a thickness of approximately 50μ was created. This film was heat treated in a hot air dryer at 150°C for 5 minutes, then immersed in boiling water for 10 minutes, and the elution loss of the film due to immersion was measured. The results are shown in Table 3.

[Table] Example 4 N-n-butoxymethylacrylamide-vinyl acetate copolymer was saponified to produce a copolymer containing 8.4 mol% of N-n-butoxymethylacrylamide units, 91.6 mol% of vinyl alcohol units, and a polymerization degree of 2250. Modified PVA was obtained. This modified PVA is insoluble in water and tends to harden into dumplings in boiling water, but completely dissolves in dimethyl sulfoxide. Add 5 parts of a 1N sulfuric acid aqueous solution to 100 parts of a 15% dimethyl sulfoxide solution of this modified PVA and cast it overnight at 80°C to form a film.
Heat treatment was performed at 150°C for 3 minutes. This film did not change its form and was insoluble even in boiling water, and did not change its form and did not dissolve even when immersed in dimethyl sulfoxide at 100°C.

Claims (1)

[Claims] 1 Formula in the molecule (Here, R ¹ is a hydrogen atom or a lower alkyl group,
R ² each represents a hydrogen atom or an alkyl group. ) A method for producing a resin with excellent water resistance, characterized in that the solvent is removed from a solution of modified polyvinyl alcohol containing the copolymerized unit represented by (2) under acidic conditions or under conditions that generate acidic substances during drying. 2. The manufacturing method according to claim 1, wherein the modified polyvinyl alcohol is a saponified product of a copolymer of N-methoxymethylacrylamide and vinyl acetate. 3. The manufacturing method according to claim 1, wherein the modified polyvinyl alcohol is a saponified product of a copolymer of Nn-butoxymethylacrylamide and vinyl acetate. 4 Claims 1 to 4 in which the solution is an aqueous solution
The manufacturing method according to item 3.