JPS6223118B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to impregnated paper using emulsion. More details on vinyl acetate and ethylene and the general formula [ _R1 : H or _CH3 , _R2 : H or an alkyl group having 5 or less carbon atoms] The weight ratio of the compound is 55-96.5:40-3:
Emulsion copolymerization using a redox catalyst using a persulfate as an initiator and a reaction product of a glyoxal compound and a salt of a reducing sulfur oxide of an alkali metal, ammonium or zinc as a reducing agent so as to have a composition of 5 to 0.5. This invention relates to impregnated paper using an emulsion obtained by Emulsions or products using emulsions obtained by emulsion copolymerization of vinyl acetate, ethylene, and an N-methylol compound or an N-alkoxy compound as a crosslinking agent have been known.For example, French Patent No. 1564100 describes vinyl acetate −
In order to increase the solvent resistance of films produced from ethylene copolymer emulsions and to improve the high mechanical stability of the films, N-
N-methylol compounds such as methylol acrylamide, N-methylol methacrylamide and their methyl or butyl ethers.
Alkoxy compound to vinyl acetate 0.5-10
% by weight and the copolymer is crosslinked at temperatures from room temperature to 180° C., preferably in the presence of a curing agent. Also US Patent No. 3345318
No. 3380851 describes the emulsion copolymerization of vinyl acetate-ethylene-N-methylolacrylamide copolymer and the use of such an emulsion for paper products with excellent water resistance and solvent resistance. . Therefore, impregnated paper using such an emulsion has excellent water resistance and solvent resistance, as well as excellent properties inherent to vinyl acetate-ethylene copolymer, that is, light resistance, heat resistance, and embossing suitability. The heat resistance and light resistance of conventional synthetic rubber latexes such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl acrylate-butadiene copolymer are poor, and the heat resistance and embossing suitability of acrylic copolymer emulsion It has been widely used in this field by improving the disadvantages of inferiority. On the other hand, the method for producing the emulsion used in such excellent impregnated paper must be a method in which vinyl acetate, ethylene, and the crosslinking agent compound are uniformly copolymerized. If it is copolymerized heterogeneously, a crosslinking reaction will occur in the crosslinking agent compound, so
Since a uniform crosslinking reaction does not occur during the crosslinking reaction, impregnated paper using such an emulsion has, for example, poor strength when wet. Therefore, in order to uniformly copolymerize vinyl acetate, ethylene, and a crosslinking agent, a method is used based on known polymerization techniques, such as adding a crosslinking agent compound continuously as the polymerization progresses. The most important thing is to maintain a constant polymerization reaction rate, ie, the desired polymerization temperature. If the polymerization temperature cannot be kept constant, not only will the desired uniform copolymer not be obtained, but the impregnation of emulsion, which plays an important role in processability and workability when manufacturing impregnated paper, for example, will be difficult. There is also the problem of making people look bad. However, the method for obtaining a homogeneous copolymer is described in the above-mentioned French Patent No. 1564100 and US Patent No. 3345318.
No. 3,380,851, redox-based catalysts with excellent polymerization temperature control properties efficiently and stably decompose the initiator at the desired polymerization temperature to generate radicals. This is a method of emulsion copolymerization using formaldehyde sodium sulfoxylate as a reducing agent to initiate polymerization. Impregnated paper using emulsion produced by this method has excellent performance as described above, but because formaldehyde sodium sulfoxylate is a compound containing formalin, products such as impregnated paper do not contain formalin. Although it is not said to emit a poisonous odor,
Toxic formalin was detected, and there was a problem in terms of safety if these products were used in applications where they would come into direct contact with the skin. Therefore, an object of the present invention is to replace the conventional redox catalyst using formaldehyde sodium sulfoxylate as a reducing agent with a novel redox-based catalyst reducing agent that has the same polymerization temperature controllability as that of the conventional redox catalyst, and to convert vinyl acetate, ethylene and to provide impregnated papers and the like using formalin-free emulsions in which the crosslinker compound is generated from uniformly emulsion-copolymerized formaldehyde sodium sulfoxylate, and the like. As a result of various studies in accordance with the purpose of the present invention, we have found that by using a reaction product of a glyoxal compound and a salt of a reducing sulfur oxide as a reducing agent for a redox catalyst, a case where conventional formaldehyde sodium sulfoxylate is used. It is possible to control the polymerization temperature in the same manner as in the previous method, to obtain an emulsion having a uniform copolymer, and because there is no formalin generated from conventional formaldehyde sodium sulfoxylate in the emulsion, it is possible to produce an emulsion using such an emulsion. It has been found that impregnated paper has excellent water resistance, solvent resistance, etc., and has the characteristics of containing little formalin, leading to the present invention. In order to achieve the object of the present invention, it is necessary and sufficient to use a reaction product of a glyoxal compound and a salt of a reducing sulfur oxide as a reducing agent for the redox catalyst, such as an alkali metal or zinc salt. When using known reducing agents such as salts of reducing sulfur oxides, amine compounds such as monoethanolamine and triethanolamine, polymerization itself may not be possible, or even if it is possible, polymerization temperature control is poor. An emulsion having a uniform copolymer cannot be obtained and the emulsion has poor impregnating properties. In the present invention, reducing agents include glyoxal compounds represented by glyoxal and methylglyoxal, and glyoxal compounds such as thiosulfuric acid, dinithionic acid,
sodium, potassium, and zinc salts of pyrosulfite;
It is a reaction product of bisulfite with a salt of an alkali metal such as sodium or potassium salt, or a reducing sulfur oxide of ammonium or zinc, and can be easily obtained by reacting the two in an aqueous solution. It is also advantageous to use such a reducing agent in combination with heavy metal salts such as iron salts and copper salts as a so-called composite reducing agent. In addition, such a reducing agent can also be synthesized during emulsion copolymerization, for example, by making a glyoxal compound exist in advance in the emulsion dispersion before the start of polymerization,
Polymerization can be carried out by adding an aqueous solution of a salt of a reducing sulfur oxide to synthesize the amount necessary for polymerization, or conversely, a salt of a reducing sulfur oxide can be made to exist in advance and a glyoxal compound can be added. Alternatively, a method can be used in which a glyoxal compound and a salt of a reducible sulfur oxide are separately added to the emulsified dispersion and polymerization is carried out while synthesizing the amounts necessary for polymerization. The amount of the reducing agent used in the present invention is not particularly limited, but is 0.25 to 3 times the amount of the commonly used oxidizing agent. Examples of the oxidizing agent used in combination with such a reducing agent in the present invention include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate. These are particularly preferably used because they also act as crosslinking aids in crosslinking reactions during the production of impregnated papers and the like. In the present invention, the general formula [A] is used as a crosslinking agent that imparts excellent water resistance and solvent resistance. [R ₁ : H or CH ₃ , R ₂ : H or an alkyl group having 5 or less carbon atoms] For example, N-methylolacrylamide, N-methylolmethacrylamide, N-alkoxymethylacrylamide, N-
Examples include methylol compounds such as alkoxyethyl acrylamide and N-alkoxybutylacrylamide, and alkyl ethers thereof having 5 or less carbon atoms. In addition, in the present invention, the copolymerization amount of the compound of general formula [A] is limited to 0.5 to 5% by weight.
The purpose is to impart a high degree of water resistance to paper impregnated with emulsion.If the amount of the compound of the general formula [A] is less than 0.5% by weight, a sufficient crosslinking effect cannot be obtained, and if the amount of the compound is less than 0.5% by weight, This is due to the inability to obtain a product that exhibits excellent performance even when polymerized. In the present invention, the ethylene content is 3 to 40% by weight.
This is because the ethylene content is sufficient to change the texture from hard to soft depending on the final performance requirements of the impregnated paper using the emulsion, and to provide sufficient water resistance strength. This is because it is necessary to copolymerize ethylene in an amount of at least 3% by weight or more, and furthermore, it is not possible to obtain a product with a soft feel even if ethylene is copolymerized in an amount of more than 40% by weight. The emulsifier used in the emulsion copolymerization in the present invention is not particularly limited, and includes various types of emulsifiers, such as completely or partially saponified polyvinyl alcohol, fibrous derivatives such as methylcellulose and hydroxyethylcellulose, and ammonium salts of α-olefin-maleic anhydride. Water-soluble polymers, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene block copolymer, various nonionic surfactants such as polyoxyethylene sorbitan fatty acid ester, lauryl sulfate ester sodium salt, dialkyl Examples include anionic surfactants such as succinates and alkylbenzenesulfonates, which may be used alone or as a mixture. Furthermore, additives such as PH regulators 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 generally the polymerization temperature should be maintained at the desired polymerization temperature in the range of 0 to 100°C, preferably in the range of 30 to 70°C. is practical. In addition, the polymerization pressure is arbitrarily adjusted depending on the amount of ethylene in the desired copolymer.
Polymerization pressures of 5 to 100 Kg/cm ² are used to obtain 40% by weight. When the emulsion obtained according to the present invention is used to manufacture impregnated paper, it may be impregnated with a conventional paper impregnation equipment and subjected to dry heat treatment. Furthermore, in addition to such emulsions, antifoaming agents, dispersion stabilizers, other known emulsions, etc. may be used in combination, if necessary. In order to obtain the effect of crosslinking reaction, the temperature is 100-180℃, preferably 130-150℃.
Heat treatment at a temperature of 1 to 5 minutes is preferable, and if necessary, a known crosslinking aid such as ammonium sulfate or ammonium chloride may be used in combination. In this way, an impregnated paper containing less formalin and exhibiting a high degree of water resistance and a high degree of sizing is obtained. 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. (1) Reference Example, Reference Example of Production of Emulsion 1 The following items were charged into a 100 pressure-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 HLB/7 polyoxyethylene nonylphenol ether 800g HLB/4 polyoxyethylene nonylphenol ether These ingredients were heated and stirred for about 1 hour to completely dissolve. . The charge was cooled to approximately 30°C before the following was 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 Purge the reactor with nitrogen and ethylene to remove oxygen. The charge was then heated to 45°C.
During the heating period, add ethylene to increase the pressure to 60Kg/cm ²
After the dissolution of ethylene in the vinyl acetate monomer reached equilibrium, an 8% aqueous ammonium persulfate solution was added at a rate of 1.4/hour. After about 5 minutes, a polymerization initiator was observed due to the reaction temperature, and the reaction temperature controller was adjusted so that the polymerization temperature was 50°C. Two feeds were then started, the first of which was 20,000 g of vinyl acetate, and the feeds were carried out at a constant rate over a period of 4 hours. The second one is 500 g of N-methylol acrylamide in 2000 g of water.
The feed was carried out at a constant rate over a period of 5 hours. During that time, set the cooling jacket temperature to 30℃, switch the ammonium persulfate charging to automatic adjustment, and set the polymerization temperature to 50℃.
The temperature was maintained at ℃. During this time, ethylene has a polymerization pressure of 60
It was kept constant at Kg/ ^cm2 . The polymerization was terminated when the amount of unreacted vinyl acetate monomer decreased to 0.32% after a polymerization time of 9.5 hours. The obtained emulsion had a solid content of 50.5% by weight,
Viscosity (BL-60RPM, 25℃) 920cps, coarse particles that cannot be filtered through a 100-mesh wire mesh 13ppm, sedimentation of 0.1ml or less, ethylene content calculated from mass balance is 25% by weight, N-methylol acrylamide content is 1.2% by weight It was %. In addition,
For sedimentation, dilute with water so that the solid content is 10wt%, put 10ml of the solution into a glass container with a 0.1ml scale, centrifuge at 3000 PRM for 30 minutes, and read the sediment. If the amount of sediment is 0.2 ml or less, the emulsion is judged to be very stable. Reference Example 2 The following items were charged into a 100 ml pressure-resistant reactor equipped with a reaction temperature controller and a stirrer. 34000g Water 365g Hydroxyethyl cellulose with 2.5 moles of ethylene oxide added 800g HLB/7 polyoxyethylene nonylphenol ether 800g HLB/4 polyoxyethylene nonylphenol ether These ingredients were heated and stirred for about 1 hour to completely dissolve. . The charge was cooled to about 30°C before the following was added. 8250 g Vinyl acetate 16 g Acetic acid 20 g Sodium acetate 0.8 g FeSO ₄ 118 g 40% glyoxal aqueous solution The reactor was parsed with nitrogen and ethylene to remove oxygen. The charge was then heated to 45°C.
During the heating period 0.78 of a 7% aqueous sodium metabisulfite solution was added. Meanwhile, ethylene was added to make the pressure 60 kg/cm ² , and after the dissolution of ethylene in the vinyl acetate monomer reached equilibrium, an 8% aqueous ammonium persulfate solution was added at a rate of 1.4/hour. After about 5 minutes, the initiation of polymerization was observed based on the reaction temperature, and the reaction temperature controller was adjusted so that the polymerization temperature was 50°C. Two feeds were then started, one was a 7% aqueous sodium metabisulfite solution, and the feeds were added at a constant rate of 0.17/hour over an 8 hour period. The other is 20,000g of vinyl acetate.
and 500 g of N-n-butoxyacrylamide, and the feed was carried out at a constant rate over a period of 5 hours. During that time, the cooling jacket temperature was set at 30°C, and the charging of ammonium persulfate was switched to automatic adjustment, allowing steady maintenance at the set polymerization temperature of 50°C. During this period, the polymerization pressure of ethylene was kept constant at 60 kg/cm ² . Polymerization was terminated when unreacted vinyl acetate monomer decreased to 0.30% 9.6 hours after the start of polymerization. The obtained ethylene-vinyl acetate copolymer aqueous dispersion had a solid content of 51.4% by weight and a viscosity (BL-
60RPM, 25℃) 960cps, 16ppm of coarse particles that cannot be filtered with a 100 mesh wire mesh, sedimentation rate of 0.1ml or less, ethylene content calculated from mass balance is
The content of Nn-butoxymethylacrylamide was 1.2% by weight. Comparative Reference Example 1 Polymerization was carried out in the same manner as in Reference Example 1, except that formaldehyde sodium sulfoxylate was used as the reducing agent in an equimolar amount with glyoxal sodium bisulfite. The polymerization time, reaction rate, and emulsion were also almost the same as in Example 1. Comparative Reference Example 2 The same procedure as in Reference Example 1 was carried out except that sodium bisulfite and glyoxal sodium bisulfite were used in an equimolar amount as the reducing agent in Reference Example 1.
After a minute had elapsed (by which time approximately 1.4 of 8% ammonium persulfate had been added), a rapid exothermic reaction occurred, and although the ammonium persulfate feed was immediately stopped and cooling started, the polymerization temperature rose to 75 °C. . Even after that, the polymerization temperature could not be controlled automatically and was carried out manually, but this control was extremely difficult and it was not possible to control the polymerization temperature at a constant level. In addition, the ethylene pressure is set to the desired ethylene content.
It was set to 65Kg/cm ² . The final emulsion had a solid content of 49.8% by weight, a viscosity of BL-60RPM,
(25℃) 460cps, coarse particles that cannot be filtered with a 100 mesh wire mesh 376ppm, sedimentation rate 0.8ml, ethylene content calculated from mass balance is 25.0% by weight, N
- Methylolacrylamide was 1.2% by weight. (2) Example The emulsions of Reference Examples 1 and 2 and Comparative Reference Examples 1 and 2 were each impregnated into Toyo Paper No. 2 (120 g/m ² ) to an impregnation rate of 25% by weight, and after air drying,
A heat treatment was performed at ℃ for 5 minutes. The performance of these impregnated papers is shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1. Vinyl acetate, ethylene and general formula [ _R1 : H or _CH3 , _R2 : H or an alkyl group having 5 or less carbon atoms] The weight ratio of the compound is 55-96.5:40-3:
Emulsion copolymerization using a redox catalyst with a persulfate as an initiator and a reaction product of a glyoxal compound and a salt of a reducing sulfur oxide of an alkali metal, ammonium or zinc as a reducing agent so as to have a composition of 5 to 0.5. impregnated paper using emulsion obtained by