JPH06280198A - Transparentizing treatment agent for paper - Google Patents

Abstract

PURPOSE:To obtain a transparentizing treatment agent for paper, suitably used for partly or wholly transparentizing an opaque paper such as wood-free paper. CONSTITUTION:This transparentizing treatment agent for paper characteristically contains, as the active component, an aqueous polymer prepared by copolymerizing a monomer mixture containing (1) 5 to 95wt.% carboxylic group- containing ethylenic unsaturated monomer and (2) 95 to 5wt.% one or more kinds of monomers selected from styrenes and (meth)acrylic acid esters and neutralizing the resultant copolymer of <=2000 molecular weight and 60-550 mgKOH/g acid value with a basic compound. The transparentizing treatment agent can uniformly transparentize a part or whole of an opaque paper such as generally used wood-free paper at low cost. In addition, the resultant transparentized paper is excellent in blocking resistance at the surface, free from reduction of strength and excellent in dimensional stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparentizing agent for paper. More specifically, it relates to a treating agent for making all or part of opaque paper such as high-quality paper transparent.

[0002]

2. Description of the Related Art Paper is normally opaque because there are voids in cellulose, which is a component of paper, and light is refracted and cannot go straight due to the difference in refractive index between cellulose and voids. . Therefore, in order to make the paper transparent, it is necessary to reduce the voids having different refractive indexes or replace the voids with a substance having a refractive index similar to that of cellulose. Conventionally, as a method of making paper transparent,
(a) Highly beating pulp fiber to reduce voids, (b) Paper impregnated with liquid substances such as oils, (c) Paper impregnated with organic solvent solution of resin After that, a method of drying, (d) a method of impregnating with a photocurable resin solution and then curing using ultraviolet rays or electron beams, and (e) a method of impregnating with an aqueous emulsion and then drying are known. .

In the paper transparency treatment, the transparency of the paper after transparency is high, there is no unevenness, the surface has good blocking resistance, the strength does not decrease, and the dimensional stability is good. Although high productivity and low cost are required, the conventional methods (a) to (e) have the following problems. In (a), the pulp fiber is beaten to a high degree so that the strength of the fiber decreases, and the paper made from it has low tear strength and insufficient transparency and poor dimensional stability. Furthermore, it is not possible to make only a part of a paper such as a general high-quality paper already made transparent.

Since (b) is impregnated with a liquid substance,
There is a problem that the impregnated liquid moves inside the paper even after the transparentization, and the transparent part is bleeding or transferred to other papers.
Also, the transparency deteriorates over time due to evaporation of the liquid substance. In (c), since an organic solvent is handled, there is a risk of fire, solvent recovery, worker safety and health, or environmental problems. In (d), the cost of photo-curable resin is high.
In addition, there is a problem that the equipment of the irradiation device for ultraviolet rays and electron beams is very expensive. In (e), since the emulsion is particles, it does not sufficiently impregnate the voids of the pulp fiber and the transparency is insufficient.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors to achieve the above object, a copolymer having a specific physical property value obtained by copolymerizing a monomer mixture having a specific composition. When a clearing agent is an aqueous polymer obtained by neutralizing water, it can be applied in an aqueous solution, so that it is excellent in safety and workability during application and drying, and of course, the transparency of the paper after treatment is improved. It has been found that the present invention is highly transparent and that a uniform transparency treatment can be performed without lowering the strength of paper, and thus the present invention has been completed.

[0006]

[Means for Solving the Problems] That is, the present invention is
(1) Carboxyl group-containing ethylenically unsaturated monomer 5 to 95
A molecular weight of 20% by weight and a monomer mixture containing 95 to 5% by weight of at least one monomer selected from (2) styrenes and (meth) acrylic acid esters.
Provided is a clearing agent for paper, which comprises an aqueous polymer obtained by neutralizing a copolymer having an oxidation of 60 to 550 mg KOH / g with a basic compound as an active ingredient. Hereinafter, the configuration of the present invention will be described in detail.

(1) Examples of the ethylenically unsaturated monomer containing a carboxyl group include monobasic acids such as acrylic acid, methacrylic acid and crotonic acid, dibasic acids such as maleic acid, itaconic acid and fumaric acid, or half-esters thereof. And the like, and acrylic acid and methacrylic acid are particularly preferable. You may use these monomers in combination of 2 or more types. Also, (2)
As styrenes and (meth) acrylic acid esters,
Examples thereof include styrenes such as styrene and α-methylstyrene, and (meth) acrylic acid lower alkyl esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. You may use these monomers in combination of 2 or more types.

The monomer mixture of the present invention contains the monomers (1) and (2) as essential components, but may contain a copolymerizable monomer (3) such as acrylamide or methacrylamide, if necessary. May be included. The usage ratio of these monomers is as follows:
5 to 95% by weight, preferably 5 to 50% by weight, monomer (2)
Is 95 to 5% by weight, preferably 90 to 50% by weight, and the monomer (3) is 0 to 50% by weight, preferably 0 to 20% by weight. In the present invention, it is necessary to produce a copolymer having a specific acid value, which is water-soluble or water-dispersible by the subsequent neutralization treatment, but since the acid value is determined by the composition of the monomer, It is necessary to select a combination of monomers and a use ratio thereof so as to obtain a desired acid value from the above range.

The copolymer of the present invention has an acid value of 60 to 550 mg K
OH / g, preferably 60 to 300 mg KOH / g. When the acid value is lower than 60 mg KOH / g, the copolymer cannot be water-soluble or water-dispersed by the neutralization treatment described later, and conversely, when it is higher than 550 mg KOH / g, The resulting transparent paper is colored yellow, which is not preferable. Also,
The molecular weight of the copolymer is 2000 or less, preferably 800 to 1900
Is. If the molecular weight is too large, the permeability of the paper will be poor and the transparency of the paper cannot be improved. The molecular weight referred to in the present invention is a value represented by a weight average molecular weight. Further, the glass transition temperature of the copolymer is preferably 0 to 150 ° C, more preferably 30 to 120 ° C. If the glass transition temperature is too low, the blocking resistance of the surface of the paper coated with the clarifying agent will be poor, and if it is too high, the film will be brittle and will crack, making it impossible to provide good transparency to the paper.

The polymerization method of the above-mentioned monomer mixture is not particularly limited, and a known general polymerization method can be adopted. For example, a typical method is a solution polymerization method in which a monomer mixture is dissolved in an organic solvent such as toluene, and heat-polymerized in the presence of a polymerization initiator. The polymerization temperature at this time is slightly different depending on the composition of the monomer,
It is usually about 70-170 ℃. As the polymerization initiator, known ones such as organic peroxides, azo compounds and redox compounds can be used, and benzoyl peroxide is generally used. The amount of the polymerization initiator used is usually 0.1 to 3% by weight, preferably 0.5 to 2% by weight, based on all the monomers.
If the amount of the polymerization initiator used is too small, not only the polymerization will not be carried out satisfactorily, but also it will be difficult to obtain a low molecular weight copolymer.

After the polymerization, the solvent can be removed from the mixture by a general method to obtain the produced copolymer. Since the copolymer having the above-mentioned physical properties obtained by the polymerization is not an aqueous polymer, it is necessary in the present invention to neutralize the copolymer with a basic compound to obtain an aqueous polymer. The basic compound may be an organic compound or an inorganic compound. Examples of the organic compound include monoethanolamine,
Examples include triethylamine and the like, and examples of the inorganic base include ammonia, sodium hydroxide, potassium hydroxide and the like. The amount of the basic compound used in the neutralization does not necessarily have to be an equimolar amount with respect to the acid value of the copolymer. If the copolymer exhibits water solubility or water dispersibility, it may be less than the equimolar amount. It doesn't matter if there are many.

Neutralization of the copolymer is 0.3
It is desirable to carry out by mixing 3 to 3 times by weight, preferably 0.5 to 2 times by weight of water and a predetermined amount of the basic compound and uniformly stirring the mixture. At this time, for example, at a temperature of 40 to 90 ° C
Heating and stirring for about 10 to 150 minutes is preferable because the neutralization reaction is efficiently promoted. In the present invention, the aqueous polymer obtained by the neutralization treatment is used as a clarifying agent. When the clearing agent is actually applied to the paper, the polymer concentration is usually 20
It is suitable that the treatment agent has a viscosity of 700 to 2500 cps in the range of 80 to 80% by weight, preferably 40 to 70% by weight. The pH of the treating agent is preferably 7.0 to 10.0, more preferably 7.5 to 9.5.

Therefore, the aqueous polymer obtained by the neutralization treatment is adjusted to the desired concentration and viscosity, if necessary. If necessary, a defoaming agent or a release agent may be added to the clarifying agent. Further, when high-speed infiltration and drying are required, or when drying at a low temperature is required, an aqueous penetration aid such as a surfactant or an aqueous drying aid can be added.

The clarifying agent of the present invention already has the normally required blocking resistance, but when higher blocking resistance is required, it is necessary to improve the surface strength by crosslinking. You can It is added with at least one cross-linking agent selected from diamines, polyamines, aziridine derivatives, diepoxy compounds, metal oxides, organic acid metal salts and metal alkoxides, which crosslinks with carboxyl groups contained in the aqueous polymer. It is achieved by Examples of the cross-linking agent include ethylenediamine, aziridine, propylene glycol diglycidyl ether, zinc oxide, zirconyl stearate, and aluminum isopropylate.

Since the clarifying agent of the present invention is an aqueous solution or an aqueous dispersion, it can be applied to paper by a conventionally known printing method. After that, the transparentizing agent penetrates by heating and drying, and transparent paper can be obtained. The coating amount on paper varies depending on the target paper quality, transparency, composition and concentration of the aqueous polymer, etc., but is about 10 to 100 g / m ² , preferably about ²⁰ to 80 g / m ² . The conditions for heating and drying are
It is usually for 30 seconds to 5 minutes at a temperature of 100 to 200 ° C.

The clearing agent of the present invention can be used for the difference in the paper to be transparentized, the copolymer concentration in the clearing agent, and the like.
By changing the conditions such as the type and amount of basic compound used for neutralization, it is possible to obtain transparent paper with high uniformity and no unevenness. Further, by using the paper transparentizing agent to which the cross-linking agent is added, the surface strength of the coating film can be increased and the blocking resistance can be set in a wide range.

[0017]

[Example 1]

(Preparation of Clarifying Agent) 100 parts of a monomer mixture consisting of 31 parts of methacrylic acid, 34 parts of methyl methacrylate and 35 parts of styrene was dissolved in 100 parts of a toluene solvent in advance, and 1 part of benzoyl peroxide was added as a polymerization initiator. Polymerization was carried out by quantitatively dropwise supplying the added solution into 100 parts of a toluene solvent whose internal temperature was controlled at 100 ° C over 5 hours, and then distilling the toluene solvent from the polymerization mixture to carry out copolymerization. Got united. This copolymer had a molecular weight of 1000 and an acid value of 130 mg KOH / g.

Next, this copolymer was mixed with triethylamine in the following proportions. Copolymer 55 parts Triethylamine 13 parts Water 32 parts Neutralization treatment is carried out by keeping this mixture at 80 ° C for 1 hour to make the copolymer water-soluble and then cooled to a concentration of 55%, viscosity of 1280 cps, pH 8.5. An aqueous polymer solution was obtained.

(Transparency treatment of paper) The above polymer aqueous solution (transparency treatment agent of the present invention) was applied to the surface of wood free paper having a basis weight of 62 g / m ^2.
After applying 50 g / m ^{2 by} printing, it was dried with a hot-air dryer at a temperature of 150 ° C for 1 minute to make the high-quality paper transparent. As a result, we were able to obtain transparency with an opacity of 24%. The opacity was measured by the paper opacity test method based on JIS P8138. When this transparent paper was left for 8 hours under a load of 500 g / cm ² in a thermo-hygrostat at a temperature of 40 ° C and a humidity of 80%, no blocking occurred and the blocking resistance was good. In addition, the strength did not decrease after transparency, and the dimensions did not change before and after coating. From this, it can be understood that the clarifying agent of the present invention is very excellent.

Example 2 (Preparation of Clarifying Agent) 100 parts of a monomer mixture consisting of 26 parts of acrylic acid, 64 parts of methyl methacrylate and 10 parts of ethyl acrylate are copolymerized in the same manner as in Example 1. As a result, the molecular weight is 1800 and the acid value is 180 mg KOH / g.
A copolymer of Next, this copolymer was mixed with ammonia water in the following proportions, dissolved and neutralized to obtain a polymer aqueous solution having a concentration of 55%, a viscosity of 2000 cps and a pH of 8.7. Copolymer 55 parts 25% Ammonia water 12 parts Water 33 parts (Transparency treatment of paper) As a result of performing the transparency treatment of high-quality paper in the same manner as in Example 1 using the above polymer aqueous solution, the opacity 21% transparent paper could be obtained. The blocking resistance, strength and dimensional stability of this transparent paper were also good.

Example 3 (Preparation of Paper Clarification Treatment Agent) 100 parts of a monomer mixture consisting of 63 parts of maleic acid monobutyl ester and 37 parts of styrene was copolymerized in the same manner as in Example 1. , Molecular weight 1600, acid value 205mg KOH / g
A copolymer of Next, this copolymer was mixed with monoethanolamino in the following proportions, dissolved and neutralized to obtain a copolymer aqueous solution having a concentration of 55%, a viscosity of 1050 cps and a pH of 7.8. Copolymer 55 parts Monoethanolamine 13 parts Water 32 parts (Transparency treatment of paper) Using the above polymer aqueous solution, the treatment for fine paper was conducted in the same manner as in Example 1, and as a result, the opacity was 20. % Transparent paper could be obtained. Moreover, the blocking resistance, strength, and dimensional stability of this transparent paper were also good.

Example 4 (Preparation of Clarifying Treatment Agent) A concentration of 55%, a viscosity of 980 cps, and a pH of 8.8 were obtained by adding the cross-linking agent solution to the polymer aqueous solution obtained in Example 2 in the following proportions. A crosslinkable copolymer aqueous solution of was obtained. Copolymer aqueous solution 98 parts 10% zinc oxide ammonia aqueous solution 2 parts (transparency treatment of paper) Using the above crosslinkable polymer aqueous solution,
As a result of performing the transparency treatment on the high-quality paper in the same manner as in Example 1, it was possible to obtain a transparent paper having an opacity of 21%. The transparent papers obtained in this example and Example 2 were heated at a temperature of 60 ° C and a humidity of 90
% When a load of 500 g / cm ² was applied for 8 hours in a constant temperature and humidity chamber, the transparent paper of Example 2 caused blocking, but the transparent paper of this Example blocked even under severe conditions. Did not wake up. This is because the surface properties have been improved by the crosslinking with zinc oxide. The strength of this transparent paper was also improved, and the dimensional stability was good.

Comparative Example (Preparation of Clarifying Treatment Agent) The same monomer mixture as in Example 1.
A solution prepared by dissolving 100 parts in 100 parts of a toluene solvent and adding 0.5 parts of benzoyl peroxide as a polymerization initiator thereto was quantitatively added dropwise to 100 parts of a toluene solvent whose internal temperature was controlled at 100 ° C over 5 hours. Polymerize by supplying
Then, the toluene solvent was distilled off from the polymerization mixture to obtain a copolymer. This copolymer had a molecular weight of 2500 and an acid value of 133 mg KOH / g. Next, this copolymer was solubilized in the same manner as in Example 1 to give a concentration of 55%, a viscosity of 2100 cps,
An aqueous polymer solution having a pH of 8.6 was obtained. (Transparency Treatment of Paper) The above polymer aqueous solution was used to perform the transparency treatment of the high-quality paper in the same manner as in Example 1. The transparency of the obtained transparent paper was 41% and sufficient transparency was obtained. Couldn't get This is because the copolymer has a large molecular weight, so that it does not permeate the fibers of the paper well and cannot sufficiently fill the voids.

[0024]

EFFECT OF THE INVENTION According to the clearing agent of the present invention, it is possible to make all or part of opaque paper, such as high-quality paper, which is generally used, transparent without unevenness. The surface has good blocking resistance, strength does not decrease, and dimensional stability is excellent. Further, since the treatment agent of the present invention is an aqueous solution, it is only necessary to carry out a transparent treatment of ordinary paper by printing and heating and drying, and as a result, there is an advantage that the productivity is high and the transparent paper can be produced at a low cost. .

Claims (2)

[Claims] 1. A carboxyl group-containing ethylenically unsaturated monomer 5 to 95% by weight, and (2) styrenes and (meth).
A copolymer having a molecular weight of 2000 or less and an oxidation of 60 to 550 mg KOH / g, which is obtained by copolymerizing a monomer mixture containing 95 to 5% by weight of at least one monomer selected from acrylate ester, A clearing agent for paper, which comprises an aqueous polymer neutralized with a basic compound as an active ingredient. 2. The paper according to claim 1, further comprising at least one cross-linking agent selected from diamines, polyamines, aziridine derivatives, diepoxy compounds, metal oxides, organic acid metal salts and metal alkoxides. Clarifying agent.