JPH0314959B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to dimensional stabilizers for paper. The essential drawback of paper whose main component is cellulose is that it expands and contracts significantly due to moisture, and improving this problem has become an important issue in the fields of printing, recording paper, and the like. Although many studies have been conducted on the elasticity of paper due to moisture, it is difficult to determine the elasticity stability due to the complex effects of pulp type, degree of beating, drying method, and many other factors. The reason for this is still not clear. Incidentally, conventionally proposed methods for stabilizing the dimensions of paper against moisture include, for example, chemically treating the hydroxyl groups of cellulose to convert them into hydrophobic groups; adding wood pulp to glass fiber, polyolefin, polyacrylonitrile, etc. paper by adding a hydrophobic substance; coating the surface of the paper with a hydrophobic substance; moderately beating the paper to loosen the entanglement of the fibers; filling with mineral filler; adding resin to make the fibers Methods such as three-dimensional bonding to prevent shrinkage during drying or drying in close contact on a large diameter cylinder are known, but in these methods,
For example, the dimensional stabilization effect is insufficient or almost ineffective, the strength of the paper is significantly reduced, the flexibility of the paper quality is inhibited, the printing characteristics are adversely affected, or the economical efficiency is poor.There are various advantages and disadvantages in practical use. It has the following problems. On the other hand, in addition to this or as a separate issue, peel-off paper for printing paper, information industry paper (computer cards, etc.), label paper, etc.
Curling caused by moisture and moisture is often a problem. Problems caused by paper curling not only reduce efficiency in industrial operations, but also affect yields and have a negative impact on profitability. Therefore, there are many complaints regarding curling of paper intermediate products. There are various causes for curling, such as the paper being directional due to mechanical cutting and becoming anisotropic, and the difference in density between the front and back sides of the paper. Curling can also occur when there is a difference in the fiber arrangement between the front and back sides of the paper, when the filler distribution is different in the thickness direction, when the internal strain is different between the front and back sides, or when the coating agent is applied only to one side. This often occurs when plastic film or aluminum foil is attached. Conventionally proposed methods for preventing curling include reducing the density difference between the front and back sides of the paper, adding fillers such as clay or talc, or using a coating agent only on one side. When applying paper, there are known methods such as coating the back side with water and drying it, adding a moisturizing agent such as glycerin or polyethylene glycol, and a softener to retain an appropriate amount of moisture in the paper and adding a softener. However, in these methods, for example,
They have advantages and disadvantages, such as insufficient or almost no anti-curl effect, reduced abrasion resistance and surface strength, adverse effects on printing properties, and poor long-term care properties, and pose various problems in practical use. ing. In view of the current situation, the present inventors have conducted various studies on methods for stabilizing the dimensions of paper and methods for preventing curling. The inventors have discovered that a specific water-soluble copolymer comprising a saturated vinyl monomer and glyoxal have excellent effects as a dimensional stabilizer or anti-curl agent for paper, and have completed the present invention. That is, the present invention provides (A) general formula [In the formula, R ₁ represents a hydrogen atom or a methyl group,
R ₂ and R ₃ may be the same or different and each represents a hydrogen atom or a lower alkyl group. ] At least one acrylamide or methacrylamide represented by (B) the general formula [In the formula, R ₁ and R ₂ represent the same thing as defined above, and n represents an integer from 2 to 50. ] At least one polyoxyethylene glycol monoacrylate or polyoxyethylene glycol monomethacrylate represented by (D) the general formula [In the formula, R ₁ represents the same thing as defined above,
R ₄ represents an alkyl group having 1 to 12 carbon atoms. ] Acrylic acid alkyl ester or methacrylic acid alkyl ester represented by the general formula [In the formula, R ₁ and R ₂ represent the same thing as defined above. ] Hydroxyalkyl ester of acrylic acid or methacrylic acid, with the general formula [In the formula, R ₁ represents the same thing as defined above. ] Acrylonitrile or methacrylonitrile represented by the general formula [In the formula, R ₁ represents the same thing as defined above,
B represents a hydrogen atom, an alkali metal salt, an ammonium salt, an amine salt or an alkanolamine salt. ] At least one water-soluble copolymer selected from acrylic acid or acrylic acid salts, methacrylic acid or methacrylic acid salts shown in the following, wherein the proportion of the copolymer of (A) is 10 to 90% by weight. , the copolymer ratio of (B) is 5 to 40% by weight, and the copolymer ratio of (C) is 5 to 40% by weight.
30% by weight and a copolymer in which the copolymer proportion of (D) is at most 30% by weight, and a dimensional stabilizer or anti-curl agent consisting of glyoxal. Examples of the acrylamide or methacrylamide monomer (A) of the copolymer component of the paper dimensional stabilizer and anti-curling agent of the present invention include acrylamide and methacrylamide [hereinafter collectively referred to as acrylic or methacrylic (methacrylic)]. ) called acrylic. ], N,N-dimethyl-(meth)acrylamide,
N,N-diethyl-(meth)acrylamide, N,
N-di-n or iso-propyl-(meth)acrylamide, etc., and acrylamide and methacrylamide are preferably used. General formula of (B) Polyoxyethylene glycol monoacrylate or polyoxyethylene glycol monomethacrylate represented by is a compound obtained by polymerizing hydroxyethyl acrylate or hydroxyethyl methacrylate with ethylene oxide, and the hydrogen atom in the terminal hydroxyl group is substituted with a methyl group, ethyl group, or propyl group. Specifically, the following can be mentioned. Examples include ω-hydroxy-poly(ethyleneoxy)-(meth)acrylate, ω-methoxy-poly(ethyleneoxy)-(meth)acrylate, and the like. Preferred hydrophobic unsaturated vinyl compounds (D) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tertiary-butyl acrylate, and acrylic acid. Acrylic acid esters such as 2-ethylhexyl, methyl methacrylate,
Ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-methacrylate
- Methacrylic acid esters such as butyl, tertiary butyl methacrylate, and 2-ethylhexyl methacrylate. Preferred hydroxyacrylates include, for example, hydroxyethyl-
(meth)acrylate, 2-hydroxypropyl-(meth)acrylate, 2-hydroxybutyl-
(Meth)acrylate. Nitriles such as acrylonitrile and methacrylonitrile are shown. Preferably, the carboxy group-containing monomer includes acrylic acid, methacrylic acid, etc., and sodium salts, potassium salts, ammonium salts, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, and ethanol. Examples include amine, diethanolamine, and triethanolamine. That is, in order to solve the above-mentioned problems as a dimensional stabilizer or anti-curl agent for paper, the present inventors have determined that the properties of the base polymer are as follows:
It must react with the crosslinking agent to form a three-dimensional network structure, it must have high moisture retention so that the water in the paper can be controlled, and the crosslinking agent must be reactive not only with the polymer but also with the paper itself. Based on the idea that glyoxal is the crosslinking agent, we selected glyoxal, and the polymer composition consists of a monomer with an amide group that reacts with the crosslinking agent [component (A)], and a monomer with an oxyethylene chain that has a high moisturizing ability. [component (B)] is selected as the main component to improve its performance as a dimensional stabilizer or anti-curling agent for paper.Furthermore, the copolymer also contains a monomer having an N-methylol group so that it reacts with the paper itself. By adding the copolymer [component (C)], the performance of the copolymer was further improved by increasing the bond between the copolymer and the paper. The composition of each monomer in the water-soluble copolymer of the present invention is that component (A) is 10 to 90% by weight and component (B) is 5 to 40% by weight.
A suitable weight % range is 5 to 30 weight % for (C) and 0 to 30 weight % for (D). That is, regarding the weight ratio of each monomer, it is preferable to have as much component (A) and component (B) as possible in order to exhibit its performance, but if one increases too much, the other and component (C) will decrease too much. ,
If component (A) is less than 10% by weight, component (B) is less than 5% by weight, or component (C) is less than 5% by weight, the respective effects will not be sufficient. Also, the amount of component (C) becomes too large, and 30
If it exceeds % by weight, cross-linking occurs between the copolymers, resulting in increased viscosity and gelation of the aqueous solution of the copolymer, which is inconvenient for use. Component (D) does not contribute to the effect as a dimensional stabilizer or anti-curl agent for paper, and may be present in the copolymer, but if the amount exceeds 40% by weight, it may cause Hydrophobization and cross-linking between copolymers occur, resulting in phase separation, high viscosity, or gelation of the copolymer aqueous solution, making it difficult to use as a dimensional stabilizer or anti-curling agent for paper. . The acrylamide polymer and glyoxal of the present invention are used as a dimensional stabilizer for coating or impregnating paper in a size press or off-machine. The amount of the specific water-soluble copolymer of the present invention added is preferably in the range of 0.1 to 15% by weight based on the weight of the pulp. The glyoxal is preferably used in a weight ratio of 0.1 to 3 parts by weight per 1 part by weight of the specific water-soluble copolymer of the present invention. If it is less than 0.1 part by weight, the dimensional stability and curl prevention effect will be low, and if it is more than 3 parts by weight, the quality of the paper will deteriorate. For anti-curl applications, it is necessary to make significant use of the water-soluble polymers of the present invention. Furthermore, during coating or impregnation, sizing agents, paper strength enhancers, etc. generally used in the paper manufacturing industry can be used in combination as appropriate. Although there are no particular restrictions on the production of the copolymer of the present invention, it is usually prepared, for example, by the following method. However, of course, it may be manufactured by other methods. In other words, the concentration of the monomer, which is the sum of components (A), (B), (C), and in some cases, component (D), is 5 to 30%.
Persulfate or a redox system of persulfate and amine or sulfite is added as a catalyst to an aqueous solution of 10 to 25% by weight, and the mixture is reacted at a temperature of about room temperature to 100° C. for about 0.5 to 5 hours. Persulfates used as catalysts include water-soluble salts,
For example, salts of sodium, potassium, ammonium, etc. are suitable, and examples of the amine include primary amines such as monoethanolamine, hexamethylenediamine, aniline, secondary amines such as diethanolamine, monomethylaniline, and triethanolamine. Any tertiary amine such as amine, dimethylaniline, or pyridinepicoline may be used. Although there is no particular restriction on the amount of catalyst used, it is usually desirable to use about 0.1 to 5.0% by weight of persulfate and 0.5 to 30% by weight of amine based on the monomer. Even if the polymerization temperature is started at room temperature, the temperature increases with the initiation of polymerization and usually reaches a final temperature of about 70°C. If the reaction starts at a temperature of about 70-80℃,
Cooling is required. The molecular weight of the copolymer in the present invention may be as low as 5,000, or as high as 2,000,000.
However, the practically suitable molecular weight is 10,000 to 100.
Copolymers in the lower range of 10,000 are preferred. Hereinafter, regarding the paper dimensional stabilizer and anti-curl agent of the present invention, the production of the copolymer, the dimensional stability,
A typical example of a test on curl prevention is shown,
This will be explained more specifically. In the following examples, "parts" mean parts by weight. Synthesis Example 1 A three-necked flask equipped with a thermometer and a nitrogen inlet tube was charged with 55 parts of acrylamide, 15 parts of polyethylene glycol monoacrylate with n=9, 15 parts of methylol acrylamide, 15 parts of acrylonitrile, and 400 parts of ion-exchanged water. After bubbling with gas for 30 minutes to remove oxygen from the system, lower the liquid temperature to 20℃.
The reaction was started by adding 10 parts of a 50% aqueous solution of redox initiator diethanolamine and 10 parts of a 20% aqueous solution of ammonium persulfate. Polymerization was continued for 1 hour after reaching 63°C, resulting in 20% of the copolymer.
% aqueous solution was obtained. The viscosity of this copolymer at 20°C was 1200 cps. Synthesis Examples 2 to 4 and Comparative Examples 1 to 5 Monomers of various compositions were reacted in the same manner as in Synthesis Example 1 to obtain various polymers. For comparison, various copolymers were prepared, including a copolymer in which the (A) component was below the lower limit (Comparative Example 1), a copolymer in which the (B) component was below the lower limit (Comparative Example 2), and (C) A copolymer in which the component is below the lower limit (Comparative Example 3), a copolymer in which the (C) component is above the upper limit (Comparative Example 4), and a copolymer in which the (D) component is above the upper limit (Comparative Example 5) were obtained respectively. These are shown in Tables 1 and 2.

【table】

[Table] A 5% aqueous solution of the water-soluble copolymer synthesized in Synthesis Examples 1 to 4 and Comparative Examples 1 to 3 was added with ion-exchanged water and glyoxal so that the solid content of the water-soluble copolymer and glyoxal was 3%. After adding glyoxal and stirring, sizeless paper with a basis weight of 60 g was impregnated with the mixture, excess liquid was wiped off with absorbent paper, and the mixture was dried at 120° C. for 5 minutes. This paper has 3.5% polymer and 3.5% glyoxal.
%. The copolymers synthesized in Comparative Examples 4 and 5 gelled or separated when made into aqueous solutions, so they could not be used for testing. This paper was used as a sample piece of 50 to 400 (mm) and left in a constant temperature and humidity chamber (20° C., 65%) for one day and night, and the water immersion elongation and air expansion/contraction rate were measured. The water immersion elongation is measured at 20°C.
Soak it in water for 10 minutes.
%) was measured. In addition, the air elongation rate is based on a sample piece at 20℃ and 33% humidity.
Change the humidity from 33% to 72%, then at 72%
The elongation rate was measured after being left for 24 hours. Similarly, the shrinkage ratio is based on 20℃ and 72% humidity.
The humidity was varied from 72% to 33%, and then at 33%.
The shrinkage rate was measured after being left for 24 hours. The results are shown in Table 3.

【table】

[Table] Expressed as total change amount.

Claims (1)

[Claims] 1 (A) General formula [In the formula, R ₁ represents a hydrogen atom or a methyl group,
R ₂ and R ₃ may be the same or different and each represents a hydrogen atom or a lower alkyl group. ] Acrylamide or methacrylamide represented by (B) General formula [In the formula, R ₁ and R ₂ represent the same thing as defined above, and n represents an integer from 2 to 50. ] Polyoxyethylene glycol monoacrylate or polyoxyethylene glycol monomethacrylate represented by (C) methylol acrylamide or methylol methacrylamide, (D) general formula [In the formula, R ₁ represents the same thing as defined above,
R ₄ represents an alkyl group having 1 to 12 carbon atoms. ] Acrylic acid alkyl ester or methacrylic acid alkyl ester represented by the general formula [In the formula, R ₁ and R ₂ represent the same thing as defined above. ] Hydroxyalkyl ester of acrylic acid or methacrylic acid, with the general formula [In the formula, R ₁ represents the same thing as defined above. ] Acrylonitrile or methacrylonitrile represented by the general formula [In the formula, R ₁ represents the same thing as defined above,
B represents a hydrogen atom, an alkali metal salt, an ammonium salt, an amine salt or an alkanolamine salt. ] At least one water-soluble copolymer selected from acrylic acid or acrylic acid salts, methacrylic acid or methacrylic acid salts, wherein the copolymer proportion of (A) is 10 to 90% by weight, The copolymer ratio of (B) is 5 to 40% by weight, and the copolymer ratio of (C) is 5 to 40% by weight.
30% by weight and a copolymer in which the copolymer proportion of (D) is at most 30% by weight, and a dimensional stabilizer or anti-curl agent consisting of glyoxal.