JPH0343400B2 - - Google Patents

Description

[Detailed description of the invention]

[1] Industrial Application Field The present invention relates to impregnated paper using a binder.
More specifically, it relates to an impregnated paper using an improved binder mainly composed of vinyl acetate and ethylene. [2] Prior art Binders obtained by emulsion copolymerization of vinyl acetate, ethylene, and an N-methylol compound or N-alkoxy compound as a crosslinking agent, or products using a binder, are known, for example, as disclosed in French Patent No. No. 1564100 discloses the use of N-methylol acrylamide and N-methylol methacrylamide as crosslinking agents to increase the solvent resistance of films produced from vinyl acetate-ethylene copolymer emulsions and to improve the high mechanical stability of the films. Using 0.5 to 10% by weight of an N-methylol compound such as and its methyl or butyl ether and an N-alkoxy compound based on vinyl acetate, the copolymer is prepared at a temperature from room temperature to 180°C.
It has been shown that the crosslinking reaction is preferably carried out in the presence of a curing agent. Also, in U.S. Patent No. 3,345,318 and U.S. Pat. No. 3,380,851,
It is described that an N-methylolacrylamide copolymer is emulsion polymerized and that such an emulsion is used as a binder for paper products with excellent water resistance and solvent resistance. In other words, impregnated paper using such an emulsion as a binder has water resistance and solvent resistance as described in JP-A No. 52-55709, as well as properties inherent to vinyl acetate-ethylene copolymer, such as light resistance and heat resistance. The heat resistance of conventional synthetic rubber latexes such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, etc. It has been widely used in this field because it improves the disadvantages of poor light resistance and poor heat resistance and embossing suitability when using an acrylic copolymer emulsion as a binder. [3] Problems to be solved As mentioned above, by copolymerizing N-methylol compounds such as N-methylol acrylamide and N-methylol methacrylamide and their N-alkoxy compounds as crosslinking agents with vinyl acetate and ethylene, Although a certain degree of improvement in water resistance and solvent resistance can be obtained, it is still unsatisfactory in many end uses, and further improvements in water resistance and solvent resistance are desired. On the other hand, products such as impregnated paper emit formalin and are not known to have a toxic odor, but if toxic formalin is detected and these products are used for purposes that involve direct contact with the skin. There was a problem with safety. That is, there is a need to further reduce formalin (residual free formaldehyde, hereinafter abbreviated as "FF") in impregnated paper, and at the same time to improve water resistance and solvent resistance. Furthermore, in order to improve water resistance and solvent resistance, it is natural to increase the crosslinking density of the binder, and for this purpose monomers involved in crosslinking such as N-methylol compounds and N-alkoxy compounds Although it is necessary to increase the content of these monomers, increasing the content of these monomers inevitably increases FF, which leads to improvements in water resistance and solvent resistance.
It has been difficult with conventional techniques to simultaneously satisfy the requirements of reducing FF. The present invention has made this possible. [4] Means for solving the problems The present invention provides [A] vinyl acetate and ethylene and the general formula (R ₁ represents H or CH ₆ , and R ₂ represents H or an alkyl group having 5 or less carbon atoms.) The monomer represented by the following is an essential component, and the weight ratio is 55 to 96.5:40 to 3:5 to 0.5, [B] a nitrogen-containing glyoxal resin that does not contain formaldehyde, and [C] a binder consisting of a metal salt catalyst. That is, by using a binder in which [A], [B], and [C] are essential, it is possible to simultaneously improve water resistance and solvent resistance and reduce FF. The copolymer emulsion [A] will be explained in detail. The monomer represented by general formula (1) is, for example, N
- Methylol (meth)acrylamide (refers to both N-methylol acrylamide and N-methylol methacrylamide; the same applies hereinafter), N
-methoxymethyl(meth)acrylamide, N
-ethoxymethyl(meth)acrylamide, N
-butoxymethyl (meth)acrylamide and the like. Note that the monomer represented by general formula (1) does not need to be one type, and may be a mixture of two or more types. Moreover, in the present invention, the copolymerization amount of the compound of general formula (1) is limited to 0.5 to 5 in terms of weight ratio.
This is to impart high water resistance and solvent resistance to impregnated paper using a binder, and the general formula (1)
If the amount of the compound is less than 0.5, a sufficient crosslinking effect cannot be obtained, and even if more than 5 is copolymerized, a product exhibiting better performance cannot be obtained. In the present invention, the ethylene copolymerization amount is limited to 3 to 40% by weight, which is sufficient to change the texture from hard to soft depending on the final performance requirements of the impregnated paper using the binder. In addition, it is necessary to copolymerize with ethylene at a weight ratio of at least 3 in order to provide sufficient water resistance, and even if ethylene is copolymerized in a weight ratio of 40 or more, the texture will be more flexible. This is due to the inability to obtain products with Note that the copolymer emulsion [A] does not need to consist only of vinyl acetate, ethylene, and the monomer represented by the general formula (1), but may also include methyl (meth)acrylate, butyl (meth)acrylate, (meth)
Various (meth)acrylic esters such as octyl acrylate and glycidyl (meth)acrylate,
Various unsaturated acids such as acrylic acid, itaconic acid, maleic acid, (meth)acrylamide, vinylsulfonic acid (or its salt), 2-hydroxyethyl (meth)acrylamide, vinyl chloride, vinylidene chloride, styrene, butadiene, acrylonitrile, It may also be one further copolymerized with diallyl esters such as maleic acid, adipic acid, and phthalic acid, triallyl esters of benzenetricarboxylic acid, multipolymerizable monomers such as triallyl isocyanurate, and the like. There are no particular restrictions on the method for producing the copolymer emulsion [A]. Examples of emulsifiers include completely or partially saponified polyvinyl alcohol, fibrous derivatives such as methyl cellulose and hydroxyethyl cellulose, various water-soluble polymers such as ammonium salts of α-olefin-maleic anhydride, polyoxyethylene alkyl ether, and polyoxyethylene alkyl. Various nonionic surfactants such as phenyl ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene sorbitan fatty acid ester, anionic surfactants such as lauryl sulfate ester sodium salt, dialkyl succinate, alkylbenzene sulfonate, etc. These are used alone or as a mixture. As the polymerization initiator, a redox initiator is preferable. Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, and various organic peroxides. Note that persulfates are particularly preferably used because they and their decomposition products also act as crosslinking catalysts. Examples of the reducing agent include formaldehyde sodium sulfoxylate, a reaction product of glyoxal and a salt of a reducing sulfur oxide, and the like. Further PH
Additives such as modifiers and electrolytes can also be used according to known emulsion polymerization techniques. There are no particular restrictions on polymerization conditions such as polymerization pressure and polymerization temperature, but
It is generally practical to maintain the polymerization temperature in the range 0 to 100C, preferably in the range 30 to 80C. In addition, the polymerization pressure is arbitrarily adjusted depending on the amount of ethylene in the desired copolymer.
A polymerization pressure of Kg/cm ² is used. The solid content concentration in the emulsion can be adjusted by adjusting the amount of monomers to be copolymerized and water, but a solid content concentration of about 40 to 60% by weight is suitable from the viewpoint of industrial use. [B] The formaldehyde-free nitrogen-containing goxal resin will be described in detail. The nitrogen-containing glyoxal resin is 4,5
-dihydroxy-2-imidazolidinone, 1-
Urea containing methyl-4,5-dihydroxy-2-imidazolidinone, 1,3-dimethyl-4,5-dihydroxy-2-imidazolidinone, etc.
N-monomethylurea, reaction product of N,N-dimethylurea and glyoxal, ethyleneurea, propyleneurea, uron, 4,5-dihydroxy-2-imidazolidinone, tetrahydro-5-(2-hydroxyethyl)- 1,3,5-
Triazin-2-one, reaction product of 5-methyl-2-pyrimidinone and glyoxal and its alkylated product or polyhydric alcohol modified product, 1,3-bis(2-hydroxyethyl)-
4,5-dihydroxy-2-imidazolidinone, formamide, N-methylformamide,
Reactive products of glyoxal and compounds having an amino group structure such as acetamide, methylene bisformamide, ethylene bisformamide, methyl carbamate, isopropyl carbamate, hydroxyethyl carbamate, acrylamide, pyrrolidone, etc., and alkylated products or polyhydric alcohol modified products thereof, etc. can be mentioned.
The glyoxal resin mentioned here is a compound collectively called a non-formaldehyde crosslinking agent in the field of fiber processing resins, but preferably 1,3
It is a glyoxal resin whose main component is -dimethyl-4,5-dihydroxy-2-imidazolidinone, and is the most practical. The metal salt catalyst [C] will be explained in detail. The metal salt is used for fiber processing (wrinkle-proofing, shrink-proofing,
Refers to metal salt catalysts used or proposed for use in permanent press processing, W&W processing, etc.). For example, magnesium salts such as magnesium chloride and magnesium nitrate, aluminum salts such as aluminum nitrate and aluminum chloride, zinc salts such as zinc nitrate, zinc sulfate, and zinc boron fluoride, tin salts such as stannic chloride, and zirconyl hydroxychloride. Examples include zirconium salts. Various types of these metal salt catalysts can be used to meet the requirements of a wide range of applications, but magnesium chloride is the most commonly used catalyst due to the balance of various properties such as little coloration of cellulose fibers, high crosslinking catalytic effect, and high safety. Magnesium chloride is the most practical metal salt catalyst. In order to meet the demands of a wide range of uses, it is naturally possible to use two or more of the metal salt catalysts exemplified above. In addition to using metal salt catalysts together, the addition of Bro/nsted acids to metal salt catalysts, regardless of whether they are inorganic acids or organic acids, is a powerful catalyst (Hot Catalyst, Activated Catalyst).
Catalyst) system,
The metal salt catalyst referred to in the present invention naturally includes this strong catalyst system. However, the other component constituting the present invention, that is, the copolymer emulsion [A], contains polymerization initiators such as persulfate, organic peroxide, formaldehyde sodium sulfoxylate, and a reaction product of glyoxal and reducing sulfur oxide. agent, lauryl sulfate sodium salt,
Bro/nsted acid is generally contained in surfactants such as alkylbenzene sulfonates, PH regulators, copolymerized monomers such as acrylic acid, maleic acid, etc. In the polymer emulsion, there is no need to intentionally add Bro/nsted acid to the metal salt catalyst to create a strong catalyst system. The Bro/nsted acids of the strong catalyst system are exemplified by citric acid, maleic acid, methanesulfonic acid, phosphoric acid, primary ammonium phosphate sulfuric acid, hydrochloric acid, aluminum dichlorohydroxide, etc., and are not particularly limited. There is no particular restriction on the ratio of the copolymer emulsion [A], the glyoxal resin [B], and the metal salt catalyst [C], but [A]:[B]:
[C]=100:1~10:0.05~4 (solid weight ratio)
is the preferred usage ratio. If [B] is less than 1 part by weight per 100 parts by weight of [A], it will be difficult to achieve the object of the present invention, and if it exceeds 10 parts by weight, the object of the present invention, namely water resistance and The effect of improving solvent resistance and FF reaches a plateau, and a large amount of [B] glyoxal resin is used unnecessarily. Furthermore, similarly for [C], if it is less than 0.05 parts by weight per 100 parts by weight of [A], it is difficult to achieve the object of the present invention, and if it exceeds 4 parts by weight, water resistance,
The effects of improving solvent resistance and FF tend to reach a plateau or decline. The above [A] copolymer emulsion and [B]
Although the glyoxal resin and the metal salt catalyst [C] have been explained, the binder of the impregnated paper contains known blowing agents, antifoaming agents, dispersion stabilizers, and wetting agents in addition to [A], [B], and [C]. and thickeners may be used as necessary, and known emulsions and latexes other than [A] may be used in combination. When producing impregnated paper using the binder obtained according to the present invention, it is sufficient to moisten the paper using ordinary paper impregnation equipment and perform a dry heat treatment, and there are no restrictions other than the composition of the binder. In addition, in order to obtain the effect of the crosslinking reaction, it is appropriate to carry out heat treatment at a temperature of 100 to 180°C, preferably 120 to 150°C for 1 to 20 minutes. Thus, low FF and high water resistance,
An impregnated paper is obtained which exhibits solvent resistance. The present invention will be explained in more detail below with reference to Reference Examples and Examples, but the present invention is not limited thereto. [5] Reference Example 1 Reference Example 1 (Production of copolymer emulsion) The following items were charged into a 100 water-resistant reactor equipped with a reaction temperature controller and a stirrer. 32000g water 365g hydroxyethyl cellulose with 2.5 moles of ethylene oxide added 800g HLB17 polyoxyethylene nonylphenol ether 800g HLB17 polyoxyethylene nonylphenol ether These materials were stirred for about 1 hour to completely dissolve. The charge was cooled to approximately 30°C before the following were added. 8250 g Vinyl acetate 16 g Acetic acid 20 g Sodium acetate 0.8 g FeSo ₄ 2880 g 8% glyoxal-sodium bisulfite aqueous solution The reactor was purged with nitrogen and ethylene to remove oxygen and the charge was heated to 45°C. During the heating period, ethylene was added to bring the pressure to 60%, and an 8% ammonium persulfate aqueous solution was added, and when polymerization started, the following two substances were started to be fed. The first was 20,000 g of vinyl acetate, and the feed was at a constant rate over 4 hours. The second one is 2000g of water.
550 g of N-methylolacrylamide was dissolved in the solution, and the feeding was carried out at a constant rate over a period of 5 hours. During this time, the polymerization pressure of ethylene was kept constant at 60 kg/cm ² . Polymerization was terminated when unreacted vinyl acetate monomer decreased to 0.32% after a polymerization time of 9.5 hours. The resulting emulsion had a solid content of 50% by weight, an ethylene content of 25% by weight, and an N-methylolacrylamide content of 1.3% by weight, calculated from mass balance. The resulting emulsion is called . Reference Example 2 (Production of copolymer emulsion) Polymerization was carried out in the same manner as in Reference Example 1, except that equimolar amounts of sodium formaldehyde sulfoxylate were used in place of glyoxal sodium bisulfite. The solid content of the resulting emulsion is 50% by weight.
The ethylene content calculated from the material balance is 25% by weight, and the N-methylolacrylamide content is
It was 1.3% by weight. The resulting emulsion is called . Reference Example 3 N-methylolacrylamide of Reference Example 1
410g, 20,000g of vinyl acetate supplied after polymerization had started was supplied after adding and dissolving 820g of N-n-butoxymethylacrylamide, and ethylene was supplied as in Reference Example ¹ , except that the polymerization pressure was 45Kg/cm2. I did the same thing. The solid content of the obtained emulsion was 50% by weight, the ethylene content calculated from the quality balance was 17% by weight, the N-methylolacrylamide content was 1.0% by weight, and the N-n-butoxymethylacrylamide content was It was 20% by weight. The resulting emulsion is called . Reference Example 4 (Production of copolymer emulsion) Vinyl acetate supplied after polymerization has started
The same procedure as in Reference Example 2 was carried out except that 2,825 g of the 20,000 g was replaced with 2-ethylhexyl acrylate. The solid content of the obtained emulsion was 50% by weight, the ethylene content calculated from the mass balance was 25% by weight, the N-methylol acrylamide content was 1.3% by weight, and the 2-ethylhexyl acrylate content was 7% by weight. It was hot. The resulting emulsion is called . Reference Example 5 (Production of nitrogen-containing glyoxal resin) 290 parts (2 mol) of a 40% glyoxal aqueous solution was adjusted to pH 6.5 with sodium carbonate. 176 parts (2 mol) of ethylene urea was added and the temperature was raised to 50±5°C.
The mixture was stirred at this temperature for about 2 hours while keeping the PH between 6 and 7. 2 hours later methanol
200 parts (6.25 moles) were added and the pH was adjusted to about 3.0 with concentrated sulfuric acid. To complete the methylation reaction, the resin solution was refluxed for 8 hours and cooled to 30°C, then the pH was brought to about 7.0 with a 25% aqueous solution of caustic soda.
The solids content was adjusted to 50% by diluting with a small amount of water. The obtained glyoxal resin is called. Reference Example 6 (Production of nitrogen-containing glyoxal resin) 363 parts (2.5 mol) of 40% glyoxal aqueous solution
The pH was made approximately neutral with a 25% caustic soda aqueous solution. Add 242 parts (2.75 mol) of dimethyl urea to 50±
The temperature was raised to 5°C. The mixture was stirred at this temperature for about 20 hours while keeping the PH between 6 and 7. Then, the mixture was cooled to 30°C, the pH was adjusted to about 5 with sulfuric acid, and the solid content was adjusted to 40% by diluting with water. The obtained glyoxal resin is called. 2 Examples 1 to 14 and Comparative Examples 1 to 20 Emulsions produced in Reference Examples...
and glyoxal resin, and magnesium chloride as a crosslinking catalyst, various formulations were made to have the solid content ratio shown in Table 1, and the water resistance, solvent resistance, and FF of these formulations were compared to paper (120 g/m ³ ) was evaluated by impregnation. The concentration of the formulation was adjusted with water, and the mixture was impregnated to an impregnation rate of 20% by weight.
After air drying, heat treatment was performed at 180°C for 10 minutes. The performance of these impregnated papers is also listed in Table 1. The test conditions are as follows. All tensile strengths are JIS
It was measured based on the paper and paperboard tensile strength test method of p-8113. (1) Dry tensile strength: Measured under standard conditions at 20℃ and 65%RH. (2) Water resistance: Tensile strength after immersion in water at 20℃ for 30 minutes. (3) Solvent resistance: Tensile strength after immersion in methyl ethyl ketone at 20°C for 30 minutes. (4) FF: Free formalin in the impregnated paper was measured according to JIS L-1041, JISL-1096 (acetylacetone method, sample 2.5 g). The performance evaluation results of impregnated paper are shown in Table 1. In all emulsions, water resistance, solvent resistance, and It is clear that FF has been improved at the same time.

【table】

[Table] [6] Results of the invention As described above, the present invention provides impregnated paper with improved water resistance, solvent resistance, and FF at the same time.

Claims (1)

[Claims] 1 [A] Vinyl acetate and ethylene and the general formula [Formula] (R ₁ represents H or CH ₆ , and R ₂ represents H or an alkyl group having 5 or less carbon atoms) A copolymer emulsion containing a monomer as an essential component and having a weight ratio of 55 to 96.5:40 to 3:5 to 0.5, [B] a formaldehyde-free nitrogen-containing glyoxal resin, and [C] a binder consisting of a metal salt catalyst. An impregnated paper characterized in that it is used. 2. The impregnated paper according to claim 1, wherein the formaldehyde-free nitrogen-containing glyoxal resin contains 1,3-dimethyl-4,5-dihydroxy-2-imidazolidinone as a main component. 3. The impregnated paper according to claim 1, wherein the metal salt catalyst is magnesium chloride. 4. The usage ratio of copolymer emulsion, formaldehyde-free nitrogen-containing glyoxal resin, and metal salt catalyst is 100:1 to 10:0.05 in solid weight ratio.
Claim 1 characterized in that ~4
Impregnated paper as described in section.