JPS6240477B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to acid-free paper with excellent sizing properties. More specifically, it does not contain aluminum sulfate and (A) a vinyl ester of a fatty acid having 6 or more carbon atoms;
At least one monomer selected from the group consisting of vinyl ethers of alkyl groups having 6 or more carbon atoms and α-olefins having 6 or more carbon atoms; (B) ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride; and (C) a water-soluble modified polyvinyl alcohol (hereinafter abbreviated as PVA) obtained by alkali saponification of a copolymer containing the three components of vinyl acetate as essential components. % by weight, and has excellent sizing properties. Paper is a hydrophilic porous material whose main raw material is pulp, but it is not practical if it is simply made from pulp. Therefore, it is necessary to use various paper chemicals such as sizing agents and fillers to produce paper that can be used for practical purposes. There are many practical physical properties of paper, among which sizing is important, such as bleeding of printing ink,
Penetration, bleeding of writing ink, and in the case of base paper for processing, are important properties that are closely related to the permeability of processing liquid and the associated physical properties of processed paper. Most of the conventionally used sized papers are produced by fixing a rosin-based sizing agent onto pulp fibers through the intervention of sulfuric acid. However, when sulfuric acid is used as a fixing agent, the paper becomes acidic due to the sulfate roots of sulfuric acid during the manufacturing process, which not only corrodes calender rolls, dryer rolls, and other metals that come into contact with the paper during the process. This may have a negative effect on the strength and durability of the paper, and may also cause problems with certain types of printing. In addition, it is widely known that a major practical problem with paper made using banal sulfate soil is that metals that come into contact with it are extremely susceptible to rust. Various measures are required to prevent rust from forming on printing paper that is used for binding. Under these circumstances, in recent years, attention has been focused on improving the size of so-called neutral paper, which is made without adding banal sulfate. On the other hand, PVA is a water-soluble polymer compound with excellent oil resistance and film-forming properties, and has been widely used as a surface sizing agent for paper and paperboard. However, it has been pointed out here that the physical properties such as Steckigt sizing are actually reduced by applying PVA. Also, CH ₂ = CHOCOCR ₁ R ₂ R ₃ (however,
R ₁ , R ₂ , R ₃ are alkyl groups) or branched fatty acid vinyl ester represented by CH ₂ =CHOR (however,
Hydrophobic group-modified PVA in which a hydrophobic group such as alkyl vinyl ether (R is an alkyl group) is introduced by copolymerization is known, and the use of these for paper processing was also reported in Japanese Patent Publications 16802-1973 and 25521-1973. Are known. However, in the case of modified PVA with only hydrophobic groups, if we try to introduce a sufficient amount of hydrophobic groups to obtain remarkable performance, it becomes water insoluble or gives an extremely high viscosity aqueous solution, which is a practical difficulty. Moreover, the fact that the foaming property was extremely high was also a serious drawback. For the reasons mentioned above, hydrophobic group-modified PVA has not yet been used for paper processing purposes. On the other hand, ionic group modification in which ionic groups such as carboxyl groups and sulfone groups are introduced into PVA
PVA is also known and their use in paper processing. Modification of these ionic groups
PVA has been put into practical use in some fields because it exhibits excellent performance through interaction with the aluminum sulfate present in paper. On the other hand, almost no denaturing effect is observed. In view of the above-mentioned circumstances, the present inventors conducted intensive research to obtain neutral paper with high size properties, and as a result, they found that they do not contain silica sulfate, and (A) contain vinyl fatty acids having 6 or more carbon atoms. ester,
At least one monomer selected from the group consisting of vinyl ethers of alkyl groups having 6 or more carbon atoms and α-olefins having 6 or more carbon atoms; (B) ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride; and (C) 0.1 to 5% by weight of water-soluble modified polyvinyl alcohol obtained by alkali saponification of a copolymer containing as essential components three components: vinyl acetate. The paper has excellent sizing, with a Steckicht sizing degree of 10 seconds or more according to JIS-P-8122, and is strong and strong because it does not contain sulfuric acid.
The present invention was completed based on the discovery that it has excellent printability and durability, and even when used in contact with metal, it does not cause any rusting on the metal. It is. Furthermore, the neutral paper of the present invention has the advantage that it can contain calcium carbonate, which is a filler for paper manufacturing that is advantageous not only in terms of performance but also in terms of economy. That is, as mentioned above, most of the rosin-based sizing agents, which are common paper-making sizing agents, are used under acidic conditions with silica sulfate, but when using the aforementioned advantageous calcium carbonate as a filler, This causes the inconvenience that calcium carbonate decomposes and foams. The neutral paper of the present invention also solves this problem, and by making it possible to use inexpensive calcium carbonate as a filler, it is possible to provide a neutral paper with excellent economic efficiency. The modified PVA contained in the neutral paper of the present invention can only be obtained by alkali saponification of a copolymer containing the above three components (A), (B), and (C) as essential components. It is surprising that a remarkable performance that could not be expected from the combination of (A) and (C) or (B) and (C) can be obtained. The fatty acid vinyl ester used in component (A) of the copolymer used in the present invention must be a vinyl ester of a so-called higher fatty acid having 6 or more carbon atoms, and a lower fatty acid having 5 or less carbon atoms. Vinyl ester is not effective enough. The reason for this is not fully clear, but it is presumed that it is due to two reasons: the hydrophobic effect is not sufficient unless the number of carbon atoms in the side chain fatty acid is larger than a certain level, and the ester bond is easily hydrolyzed during alkali saponification. Ru. Vinyl esters of fatty acids having 6 or more carbon atoms that can be used in the present invention include capric acid vinyl ester, lauric acid vinyl ester, stearic acid vinyl ester, 1,1,3,3-tetramethylbutyric acid vinyl ester, 2. Examples include 2,4,4-tetramethylvaleric acid vinyl ester and other saturated branched fatty acid vinyl esters, but especially those with a tertiary or quaternary carboxyl group.
Preferred are saturated branched fatty acid vinyl esters which are present in the α-position relative to the carbon atoms of the same class. Examples of the vinyl ether of an alkyl group having 6 or more carbon atoms used in component (A) of the copolymer used in the present invention include octyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether, and the like. When a vinyl ether having an alkyl group having 5 or fewer carbon atoms is used, the effect is insufficient, probably because of its weak hydrophobicity. The α-olefins having 6 or more carbon atoms used in component (A) of the copolymer used in the present invention include heptene-1, dodecene-1, octadecene-1, and other ethylene telomerization products. Examples include the resulting α-olefins having 10 to 25 carbon atoms and mixtures thereof. In the case of α-olefin, the effect begins to become apparent when the number of carbon atoms in the side chain is 4 or more, that is, the total number of carbon atoms in the monomer is 6 or more. Examples of the ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride used in component (B) of the copolymer used in the present invention include acrylic acid, methacrylic acid, crotonic acid, maleic acid,
Examples include fumaric acid, itaconic acid, citraconic acid, their lower alkyl esters such as methyl or ethyl, and their acid anhydrides, among others, maleic acid, fumaric acid, itaconic acid, citraconic acid, etc. Dicarboxylic acids and their lower alkyl esters or acid anhydrides are more effective, and itaconic acid, maleic anhydride, and monomethyl maleate are particularly excellent in practice. The proportion of each component in the copolymer containing the above-mentioned components (A), (B), and (C) as essential components used in the present invention is determined by the number of carbon atoms in the hydrophobic group, the ethylenically unsaturated The proportion of component (A) in the copolymer should be selected appropriately depending on the molecular structure of the carboxylic acid derivative, etc., but from the viewpoint of water solubility and performance when used for coating processing, the proportion of component (A) in the copolymer should be 0.2 to 10 mol. %, more preferably 0.8 to 7 mol%, and the proportion of component (B) varies depending on the content of component (A).
A suitable amount is 0.1 to 10 mol%, preferably 0.3 to 5 mol%. Further, the preferred ratio of the mole percent of component (B) to the mole percent of component (A) is usually 0.2 to 3.0, but is not limited to this range. There are no particular difficulties in producing the modified PVA used in the present invention, and conventionally known polymerization methods and saponification methods can be applied. In other words, as a polymerization method, components (A), (B), and (C) are added to a polymerization system all at once, in parts, or continuously depending on their respective copolymerization reactivity ratios, and the In a medium or in the presence of lower alcohols such as methyl alcohol and ethyl alcohol, 2.
A method of polymerization using a radical polymerization catalyst such as 2'-azobisisobutyronitrile or benzoyl peroxide can be applied. Many known methods used for saponifying polyvinyl acetate copolymers can be used to alkali saponify the copolymer containing components (A), (B), and (C) obtained in this way. However, usually sodium alcoholate, caustic soda,
A suitable method is saponification using an alkali such as caustic potash. As the alcohol, lower alcohols such as methyl alcohol and ethyl alcohol are particularly suitable. Further, these alcohol solvents may contain 40% by weight or less of a low dielectric constant solvent such as acetone, methyl acetate, ethyl acetate, or benzene. Saponification using a conventionally known acidic compound (so-called acid saponification) cannot be employed in the present invention because when applied to the copolymer of the present invention, the modified PVA tends to become water-insoluble. The degree of polymerization of the modified PVA used in the present invention should be appropriately selected depending on the purpose of use, but is usually 200%.
A range of ~3000 is appropriate. Furthermore, the degree of saponification of the vinyl acetate ester component can be selected as long as it does not impair water solubility, but it is usually recommended to use a highly saponified product of 97 mol% or more in terms of water resistance and strength. Although desirable, partially saponified products can also be used depending on the purpose of use. In the present invention, the modified PVA needs to be contained in an amount of 0.1 to 5% by weight based on the paper, for example, by a method such as coating, although this will vary depending on the required performance of the paper. If it is less than 0.1% by weight, no remarkable performance will be exhibited. Moreover, using more than 5% by weight is not desirable for general purposes because it increases the cost of raw materials and chemicals. When applying, the modified PVA of the present invention is usually used alone as an aqueous solution, but it may be mixed with carboxyl group-containing PVA, other modified PVA, or even a small proportion of unmodified PVA to the extent that the purpose of the present invention is not impaired. It can also be used. Further, for the purpose of preventing adhesion to the drying roll after coating, a release agent selected from the group consisting of starch, wax emulsion, and various activators may be used in combination. Other synthetic water-soluble polymers such as polyhydric alcohols such as glycerin, diethylene glycol, and ethylene glycol, plasticizers, carboxymethyl cellulose, starch, and their derivatives, styrene-maleic anhydride copolymers, and styrene-acrylic acid copolymers. Furthermore, mineral pigments such as calcium carbonate, kaolinite clay, loite clay, and satin white can also be used in combination. Coating methods include size press, calendar size, tab size, gate roll coater, knife coater,
Any conventionally known method such as a blade coater can be used. The base paper used to obtain the neutral paper of the present invention may be obtained from softwood pulp, hardwood pulp, or a mixture thereof, and may further contain other fibers such as synthetic fibers, man-made fibers, and synthetic pulp. Moreover, not only virgin pulp but also broken paper, waste paper, etc. may be mixed. Furthermore, there is no problem in containing paper chemicals commonly used in the production of neutral paper, such as paper strength enhancers, drainage accelerators, antifoaming agents, clays, and fillers such as calcium carbonate. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Note that "Example Middle" is based on weight unless otherwise specified. Example 1 (1) Preparation of Sample No. 1 In a polymerization can, 2100 parts of vinyl acetate, 110 parts of saturated branched fatty acid vinyl ester with an average carbon number of 10 (manufactured by Ciel Chemical Co., Ltd., trade name VeoVa-10), and 1.1 parts of itaconic acid were added. and 1750 parts of methyl alcohol. Next, the system was stirred while passing a nitrogen gas flow into the polymerization reactor, and when the temperature was raised to 60°C, α・α′-azobisisobutyronitrile 6.0
to start polymerization. From the start of the polymerization, 170 parts of a methyl alcohol solution containing 26.0 parts of itaconic acid was continuously added dropwise over 4 hours depending on the polymerization rate of the polymerization system, and the polymerization was carried out.
Polymerization is terminated when the polymerization rate of vinyl acetate reaches 75%. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing methyl alcohol vapor to obtain a methyl alcohol solution of the copolymer. Then add to the solution
A methyl alcohol solution containing 38 parts of sodium hydroxide was added, stirred thoroughly, and left to stand for a saponification reaction, and the precipitated gel was crushed.
After washing and drying, a white PVA copolymer was obtained. As a result of analysis using nuclear magnetic resonance absorption spectroscopy and conductivity titration, it was found that it contained 2.2 mol% of VeoVa-10 component and 1.1 mol% of itaconic acid component, and 98.5% of the vinyl acetate component was saponified. It was denatured PVA. In addition, the degree of polymerization was determined from the intrinsic viscosity number in dimethyl sulfoxide containing potassium nitrate, and it was found to be 620.
It was hot. (2) Preparation of Samples No. 2 to No. 5 (A) Use VaoVa-10 (manufactured by Schiel Chemical) or lauryl vinyl ether as the component, and use maleic anhydride or crotonic acid as the (B) component instead of itaconic acid. A polyvinyl alcohol copolymer was obtained using a method similar to that used for preparing sample No. 1. The analytical values and other results are shown in Table 1. (3) Preparation of comparative samples No. 6 to No. 12 (A) Using VeoVa-10 (manufactured by Ciel Chemical) or octyl vinyl ether as the component, using maleic anhydride or crotonic acid as the (B) component, and (A) Comparative samples were prepared using either component () or component (B), or by using the same method as sample No. 1 without using both.
No. 7 to No. 12 were obtained. Comparative sample No. 6 was prepared in the same manner as sample No. 1 using butyl vinyl ether as the (A) component and maleic anhydride as the (B) component. The analytical values and other results are summarized in Table 1. In addition, comparative samples No. 7 and No. 8 did not dissolve in either hot water or cold water, so
Subsequent performance evaluation was not possible.

[Table] (4) Performance evaluation Paper made using a hand paper machine using bleached softwood kraft pulp (NBKP) beaten to a freeness of 590 c.c. without adding banal sulfate soil, basis weight 65
A base paper of g/m ² was obtained. Prepare a 4% aqueous solution of the sample obtained above, add a small amount of antifoaming agent (Pionin K-17 manufactured by Takemoto Yushi Co., Ltd.), and apply the solids coating amount to the base paper obtained earlier using a lab size press. 1.0g/
After coating to a thickness of m ² and drying, heat at 20°C and 65°C.
After being left in a test room at %RH (relative humidity) overnight, it was subjected to physical property measurements. In addition, when performing size press coating, the generation of bubbles in the liquid circulation path was observed and compared. The results are summarized in Table-2.

【table】

[Table] From the results shown in Table 2, the neutral paper of the present invention not only has an extremely excellent Steckigt sizing degree, but also that the modified PVA used in the present invention has a hydrophilicity due to the effect of the hydrophobic component (A). It can be seen that the effect of component (B) acts synergistically to provide a sizing method with little foaming during coating and extremely excellent workability. On the other hand, even if it contains both a hydrophobic component (A) and a hydrophilic component (B), the degree of Stekicht sizing is low for alkyl vinyl ethers in which the hydrophobic component has 5 or less carbon atoms, as seen in sample No. 6. It doesn't get too expensive.
Furthermore, comparative sample No. containing only the hydrophobic component (A).
In the case of No. 7, No. 8, and No. 9, they have serious drawbacks such as being water-insoluble and having a large foaming property and not having good workability. Comparative samples No. 10 and No. 1 containing only the hydrophilic component (B).
In the case of 11, there is no noticeable improvement in size. Comparative sample No. 12, which does not have either the hydrophobic component (A) or the hydrophilic component (B), does not show any significant sizing effect. Example 2 Basis weight 64 containing 10% calcium carbonate using a 3:1 mixed pulp of softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP)
A base paper of g/m ² was obtained. A 7% aqueous solution of the sample obtained in Example 1 was prepared, a small amount of antifoaming agent (Pionin K-17 manufactured by Takemoto Yushi Co., Ltd.) was added, and the solid content coating amount was measured using a lab size press on the base paper obtained earlier. It was size-press coated to a density of 2.8 g/m ² , dried, and left in a test room at 20° C. and 65% RH overnight, after which the Steckigt sizing degree was measured according to JIS p-8122. Table 3 summarizes the results of observation and comparison of bubble generation in the liquid circulation path when performing size press coating. From the results shown in Table 3, the neutral paper of the present invention is a neutral paper containing calcium carbonate as a filler and has an extremely high Steckigt sizing degree, as well as the modified paper used in the present invention. Effect of hydrophobic component (A) and hydrophilic component (B) of PVA
The effects of the above work synergistically to provide a sizing method with very little foaming during coating and excellent workability. On the other hand, samples No. 7 and No. 7 containing only the hydrophobic component (A)
In the case of No. 8 and No. 9, there are serious drawbacks in that they are water-insoluble and have a large foaming property, making stable work impossible. Samples No. 10 and No. 11 containing only the hydrophilic component (B) and sample No. 12 containing neither the hydrophobic component (A) nor the hydrophilic component (B) exhibit no size effect at all. Even if it contains both a hydrophobic component (A) and a hydrophilic component (B), only sample No. 6 has butyl vinyl ether, which is an alkyl vinyl ether in which the hydrophobic component (A) has 5 or less carbon atoms in the side chain. As expected, the Steckicht size degree is low.

[Table] Example 3 Modification obtained in Example 1 to the base paper obtained in Example 2
Size press coated with a 5:5 mixture of PVA and starch at 2.5g/m ² and dried at 20℃, 65%
After being left in a RH (relative humidity) test room overnight, JIS
Steckcht size was measured according to p-8122. The results are shown in Table-4. While the sizing degree of the base paper was 0 seconds, the neutral paper of the present invention had a high sizing degree of 11 to 22 seconds. Furthermore, foaming properties during application were extremely low.

【table】

Claims (1)

[Scope of Claims] 1. A vinyl ester of a fatty acid containing no carbon sulfate and (A) having 6 or more carbon atoms;
At least one monomer selected from the group consisting of vinyl ethers of alkyl groups having 6 or more carbon atoms and α-olefins having 6 or more carbon atoms; (B) ethylenically unsaturated carboxylic acid or its lower alkyl ester or acid anhydride; and (C) 0.1 to 5% by weight of water-soluble modified polyvinyl alcohol obtained by alkali saponification of a copolymer containing as essential components three components: vinyl acetate. Acid-free paper with a certain size. 2 Component (A) is a branched fatty acid vinyl ester that contains a tertiary or quaternary carbon atom and has a carboxyl group at the α-position with respect to the carbon atom, and component (B) is The neutral paper having excellent sizing according to claim 1, which is a saturated dicarboxylic acid or its lower alkyl ester or acid anhydride. 3. The neutral paper having excellent sizing according to claim 2, wherein component (B) is maleic acid, maleic ester, or maleic anhydride. 4. A neutral paper having excellent sizing according to claim 2, wherein component (B) is itaconic acid.