JPH03234754A - Composition, and coating material for paper - Google Patents

Abstract

PURPOSE:To avoid the viscosity increase of coating soln. and agglomeration of pigment and improve water resistance, barrier properties, etc., by compounding a vinyl alcohol polymer, a polyamide-epichlorohydrin resin, and a polyethyleneimine. CONSTITUTION:A compsn. is prepd. by compounding 100 pts.wt. vinyl alcohol polymer having a degree of polymn. of 100 or higher and a degree of saponification of 70mol% or higher and comprising a carboxyl-modified polyvinyl alcohol pref. having a degree of modification by the group of 0.1-20mol%, 5-100 pts.wt. polyamide-epichlorohydrin resin obtd. by reacting a polyamide resin with epichlorohydrin, 1-30 pts.wt. polyethyleneimine having a mol.wt. of 200-500000, and, if necessary, 1-50 pts.wt. alkaline earth metal compd. The compsn. is used as a coating material for paper and an overcoating material for thermal recording paper.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Local glue The present invention relates to a composition and a paper coating agent using the same. More specifically, the present invention relates to a coating agent for paper that has a property of imparting a high level of surface strength, water resistance, and properties of low air, oil, or organic solvent absorption and permeability, that is, barrier properties, to paper.

B. Prior Art Conventionally, polyvinyl alcohol polymers (hereinafter sometimes abbreviated as PVA) have been used as clear coating agents to improve paper surface properties, such as improving surface strength, smoothness, gloss, or barrier properties. It is also widely used as a binder in pigment coatings. PVA
is widely known to have excellent film-forming properties and strength that are unrivaled by other adhesives.

However, in recent years, there has been a demand for PVA that further improves the surface properties of paper due to the tendency for surface strength to decline due to an increase in the proportion of paper coated in pulp raw materials, or for the tendency to increase printing speed. .

Furthermore, thermal recording paper, which has seen great development in recent years, can cause background coloring or sweat from hands when exposed to an ammonia atmosphere or an organic solvent atmosphere, such as when copying blueprints, after coloring the image.
It has drawbacks such as the skin becoming dirty and letters and images disappearing due to the effects of oil in food and plasticizers in plastic.

Furthermore, if the paint is stored or used in humid conditions or if water is spilled on it, the paint film will become sticky or run off, so it is necessary to make the paint film water-resistant.

Traditionally, in order to improve the water resistance and barrier properties of paper,
Various proposals have been made to provide a protective layer on the surface layer of paper.

However, in addition to water resistance and barrier properties, there is no formulation that improves water resistance and barrier properties at a drying temperature of 50°C or less without impairing heat-sensitive properties, increasing the viscosity of the coating group, or aggregating pigments. It has not been discovered yet.

Problems to be Solved by the Invention The object of the present invention is to provide a composition and a coating agent using the same that are completely free from such problems.

D. In order to resolve the problem, the inventors of the present invention have conducted extensive studies to improve this drawback, and have found that by applying a composition containing PVA, polyamide epichlorohydrin resin, and polyethyleneimine as main components to paper as a coating liquid, He discovered that when an alkaline earth metal compound is used in combination with PVA when dissolving it, it has particularly excellent water resistance, and also significantly improves the surface properties such as surface strength and barrier properties of paper, thereby completing the present invention. reached.

The present invention will be explained in detail below.

The PVA used in the coating agent of the present invention is not particularly limited as long as it can be obtained by saponifying polyvinyl ester obtained by polymerizing vinyl ester in a predetermined method using a conventional method, but it further enhances the effects of the present invention. For this purpose, carboxyl group-modified PVA is particularly desirable. Carboxyl group-modified PVA is vinyl ester and
Ethylenically unsaturated dicarboxylic acids or esters thereof, such as maleic anhydride, maleic acid monoester, maleic acid noester, itaconic acid, itaconic acid monoester,
It is obtained by saponifying a copolymer of monocarboxylic acids such as crotonic acid and acrylic acid, and (meth)acrylic acid esters. In the present invention, carboxyl group-modified PVA includes those containing a carboxyl group or a salt thereof in the molecule, but even if it does not contain a carboxyl group, it has groups that can become carboxyl groups during dissolution or use, such as lactone groups and esters. Those having groups are also included in this range. In addition, the degree of modification of carboxyl group is 0.
．． It is 1 to 20 mol%, preferably 0.2 to 5 mol%.

There is no particular restriction on the degree of polymerization of PVA of the present invention, but 1
00 or more, particularly 500 or more is preferably used. The degree of saponification of PVA is not particularly limited as long as it is within the range of water solubility, but it is usually 70 mol% or more, preferably 80 mol% or more.

In addition to the carboxyl group, PVA used in the present invention has a sulfonic acid group, an ammonium group, and a carbon number of 4 to 18.
It may contain a small amount of 10 mol % or less of a reactive group such as a hydrophobic group, an amide group, an acetoacetyl group, or a silanol group.

Further, the polyamide epichlorohydrin resin used for crosslinking PVA, particularly carboxyl group-modified PVA, at room temperature is obtained by reacting epichlorohydrin with a polyamide resin obtained by condensation of an alkyl polyamine compound and a dicarboxylic acid. It is a resin that has an Epoquin group or a chlorohydrin group in its molecule. In addition, polyethyleneimine has the effect of promoting crosslinking reactions, and has a molecular weight of 200 to s.
oo ooo, especially those with a number of 600 to 100,000 are preferably used.

Furthermore, alkaline earth metal compounds used to improve the effects of the present invention, particularly water resistance, include hydroxides, salts with weak acids, and chlorides of beryllium, magnesium, calcium, strontium, zinc, etc. , especially calcium hydroxide and magnesium hydroxide.

The mechanism of this action is unknown, but by adding it when dissolving carboxyl group-modified PVA, it hydrolyzes the lactone rings and ester groups in PVA to carboxyl groups, increasing the number of groups that can participate in the crosslinking reaction. Since it is sufficiently effective even in the case of unmodified PVA, it is thought that some kind of action such as chelate bonding is involved.

The composition ratio of these compositions is 100 parts of PVA (in terms of pure content).
Parts refer to parts by weight. (same below), the polyamide epichlorohydrin resin is 5 to 100 parts, preferably 20 to 100 parts.
70 parts, polyethyleneimine in 1 to 30 parts, preferably 5 to 20 parts, and alkaline earth metal compound in 1 to 50 parts, preferably 5 to 20 parts.

Known additives such as ordinary plasticizers, antifoaming agents, mold release agents, etc. can also be added to the coating agent of the present invention, if necessary. Furthermore, other known coating agents such as modified PVA, starch, CMC, or various synthetic resin emulsions may be mixed. Further, although the coating agent is generally suitably used for clear coating of paper, it can also be used for pigment coating by adding pigments such as fur, calcium carbonate, titanium dioxide, etc. as appropriate.

There are no particular restrictions on the paper to be coated with the paper coating agent of the present invention, but examples include paperboards such as manila pole, white ball, liner, printing paper such as general wood-free paper, medium-quality paper, gravure paper, and release paper. , information processing paper, etc.

Among these, it is suitably used as a coating agent for overcoating heat-sensitive recording paper, which requires particularly high water resistance and barrier properties.

When applying the coating agent to such paper, the concentration of the water-soluble group is preferably 20% by weight or less as a solid content, preferably 3.
~15% by weight is suitable.

For coating this, any known method such as a size press, roll coater-air knife coater, blade coater, etc. can be employed.

The coating amount varies widely depending on the guideline and is not particularly limited, but it is usually 0.01-30g/m', preferably 0.05g/m'.
~5 g/m' is implemented.

EXAMPLES The present invention will be specifically described below with reference to Examples. However, unless otherwise specified, "parts" and "%" in the examples are "parts by weight" and "% by weight," respectively.

Example 1 Polyvinyl alcohol 10% aqueous solution 100 with a degree of polymerization of 1800, a degree of saponification of 88 mol%, and a degree of itaconic acid modification of 1 mol%
24 parts of a 12.5% aqueous solution of polyamide epichlorohydrin resin was added to 1 part, and then 0.5 part of polyethyleneimine was mixed to give a 10% solids concentration.The coating solution was coated onto commercially available facsimile thermal paper at 4 g/m2. "After coating using a bar coater, it was dried for 5 minutes in a hot air dryer at 50°C. Thereafter, barrier properties and water resistance were tested by the methods shown below. The results are shown in Table 1.

) Barrier properties: One drop of acetone was dropped onto the treated thermal recording paper to determine the degree of color development.

- A piece of blue-printed copy paper was placed on top of the treated thermal recording paper to determine the presence or absence of background stains.

i) Water-resistant treated thermal recording paper was cut into lam-width pieces, immersed in water at 60°C for 16 hours, taken out and rubbed with a fingertip on a black film to determine the degree of elution.

Example 2 Polyvinyl alcohol with a degree of polymerization of 1800, a degree of saponification of 88 mol%, and a degree of modification with maleic acid of 0.5 mol% was heated and dissolved with calcium hydroxide at a solid content ratio of 10% to form a 10% solution. was created.

A coating solution was prepared by mixing polyamide epichlorohydrin resin and polyethyleneimine in the same manner as in Example 1, and the test was conducted in the same manner as in Example 1 except that it was coated on commercially available facsimile thermal paper using a bar coater. did. The results are shown in Table 1.

Example 3 Calcium hydroxide having a solid content ratio of 10% was heated and dissolved in polyvinyl alcohol having a degree of polymerization of 1750 and a degree of saponification of 87 mol% to prepare a 10% solution.

A coating solution was prepared by thoroughly mixing polyamide epichlorohydrin resin and polyethyleneimine in the same manner as in Example 1, and the coating solution was coated on commercially available facsimile thermal paper using a bar coater. I tested it. The results are shown in Table 1.

Comparative Example 1 10% aqueous solution of polyvinyl alcohol with a degree of polymerization of 1800, a degree of saponification of 88 mol%, and an itaconic acid modification degree of 1 mol%.
Same as Example 1 except that a coating solution made by mixing 0 parts of polyamide epichlorohydrin resin with 24 parts of a 12.5% aqueous solution to give a solid content concentration of 10% was coated on commercially available thermal paper for facunmilling using a bar coater. I tested it.

The results are shown in Table 1.

Comparative Example 2 A test was conducted in the same manner as in Comparative Example 1 except that the degree of saponification of the itaconic acid-modified polyvinyl alcohol used in Comparative Example 1 was changed to 98 mol%. The results are shown in Table 1.

Comparative Example 3 An LO% aqueous solution was prepared by heating and dissolving 10% solids calcium hydroxide in itaconic acid-modified polyvinyl alcohol having a degree of polymerization of 1800 and a degree of saponification of 98 mol%. This is polyamide epichlorohydrin resin 12
．． Example 1 except that a coating solution was prepared by mixing 24 parts of a 5% aqueous solution and coated on commercially available facsimile thermal paper.
I tested it in the same way.

The results are shown in Table 1.

Comparative Example 4 A 10% aqueous solution of polyvinyl alcohol having a degree of polymerization of 1750 and a degree of saponification of 88 mol% was prepared. A test was conducted in the same manner as in Example 1, except that this was used to coat with the same composition as in Comparative Example 3. The results are shown in Table 1.

Comparative Example 5 Polymerization degree 1800. 10% polyvinyl alcohol aqueous solution 1 with saponification degree of 98 mol% and itaconic acid modification degree of 1.0 mol%
A coating was prepared by adding 7.5 parts of a 40% glyoxal aqueous solution to 0.00 parts and tested in the same manner as in Example 1, except that it was coated on commercially available facsimile thermal paper. The results are shown in Table 1.

1) 2) Barrier properties: ○: No color development or discoloration.

×: Color development and discoloration.

△: Between ○ and X.

Water resistance: 5: No elution.

1: Elutes pure white.

2-4: between 5 and 1.

As shown in Table 1, it can be seen that the thermal recording paper overcoated with the composition according to the present invention has significantly better barrier properties and water resistance than conventional products.

Example 4 Kaolin clay and synthetic silica were mixed at a composition ratio of 1:1.
1 part and 0.3 part of sodium polyacrylate were thoroughly stirred and dispersed using a mixer to obtain a 60% pigment slurry.

A 10% solution obtained by adding calcium hydroxide at a solid content ratio of 10% to polyvinyl alcohol with a degree of polymerization of 1750 and a degree of saponification of 87 mol % and heating and dissolving it is converted into a solid state with a ratio of pigment to polyvinyl alcohol of 1=1. After mixing the pigment slurry at a solid content ratio of 40 parts and 10 parts of polyamide epichlorohydrin resin and polyethyleneimine to polyvinyl alcohol, respectively, the solid content concentration was 2.
A 0% coating solution was prepared.

The paste was coated on high-quality paper using a size press machine at 8 g/m" and dried for 2 minutes in a hot air dryer at 100°C.
After one week of humidity control under conditions of 0°C and 65% RH, 60°C and 5%
A lightweight coated paper was produced by calendering under the conditions of 0 kg/c+a' and 1011/a+in. This lightweight coated paper was tested for water resistance, surface density, and suitability for offset printing using the following methods. The results are shown in Table 2.

Water resistance: After wetting the coated surface with water for 1 minute, apply 10% water resistance with your fingertips.
The degree of elution by repeated rubbing was determined.

Surface density: The printing speed at which paper peeling occurs on the coated surface was determined using an IGT printability tester.

Offset printing suitability: Printing was performed using a test offset printing machine to determine whether the printability was good or bad.

Comparative Example 6 Example 4 except that the formulation of Example 4 did not contain polyethyleneimine and that polyvinyl alcohol was dissolved alone without using calcium hydroxide.
Tested with similar composition and method. The results are shown in Table 2.

Comparative Example 7 Polyvinyl alcohol 10% water solution with a degree of polymerization of 1750 and a degree of saponification of 98 mol% was used in Example 4 at 60% so that the ratio of pigment to polyvinyl alcohol was a solid content ratio of 1.
After mixing the pigment slurry, a test was conducted in the same manner as in Example 4, except that glyoxal was added at 10% (solid content ratio) to polyvinyl alcohol and a coating liquid with a solid content concentration of 20% was used. . The results are shown in Table 2.

l: Elutes pure white.

2 to 4, between 5 and 1.

2) Surface strength, measurement results using IGT printing suitability tester 3
) Suitable for offset printing; ○: Good.

×: Defective.

△: Between ○ and ×.

The composition used in the present invention consisting of PVA, polyamide epichlorohydrin resin and polyethyleneimine, and if necessary, an alkaline earth metal compound used together with PVA during dissolution, can be applied to paper as a coating agent to provide excellent properties. By applying the organic solution to the paper as a coating agent, it not only provides excellent water resistance but also has extremely excellent barrier properties against organic solvents and the atmosphere.

In particular, water resistance does not require strong heat treatment, for example,
Excellent water resistance is exhibited even under dry conditions below ℃. Furthermore, the composition of the present invention has the advantage that even if the mixed solution is left for a long time, no increase in viscosity or layer separation occurs, and the effects such as water resistance and barrier properties of paper coated with the composition left undisturbed are the same as immediately after preparation. .

Claims (5)

[Claims] (1) A composition comprising a polyvinyl alcohol polymer, polyamide epichlorohydrin resin, and polyethyleneimine. (2) A composition comprising a polyvinyl alcohol polymer, a polyamide epichlorohydrin resin, polyethyleneimine, and an alkaline earth metal compound. (3) The composition according to claim 1 or 2, wherein the polyvinyl alcohol polymer is a carboxyl group-modified polyvinyl alcohol. (4) A paper coating agent comprising the composition according to any one of claims 1 to 3. (5) A coating agent for overcoating thermal recording paper, comprising the composition according to any one of claims 1 to 3.