JPS58220893A - How to prevent paper from curling - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing curling of paper, and more particularly, to preventing curling of paper coated on one side, such as release paper, recording paper, and the like.

Conventionally, paper materials such as release paper that have been treated with resin on one side tend to curl due to changes in humidity, etc.
A thermosetting paint layer is provided on the unprocessed side, that is, the back side, to prevent curling. However, due to longevity, the conventional method requires a relatively thick anti-curl layer, which increases the weight of the paper and is not economical.

The present invention solves the drawbacks of the prior art, and involves applying a photocurable paint containing a monomer and/or oligomer having 93 or more functional groups per molecule to the back side of paper and curing it. This is a paper curl prevention method characterized by the following.

To explain the present invention in detail, the coated paper to which the method of the present invention is applied includes, for example, release paper, water-repellent paper, art paper, coated paper, waterproof paper, wax-treated paper, machine-finished paper - super finish Paper, pound paper, carton paper, glassine paper,
These include recording paper (electrophotographic paper, discharge recording paper, magnetic recording paper, 7 heat-sensitive recording paper, etc.) and various composite papers, etc., which have been subjected to coating treatment on one side.

The photocurable paint used in the present invention forms a film with extremely high crosslink density, with three or more crosslinks in one molecule.
Preferably, a monomer and/or oligomer having four or more functional groups (addition-polymerizable double bonds) is an essential component. Examples of such polyfunctional oligomers include dipentaerythritol hexa(meth)acrylate, tetraglycidyl ether (meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ) acrylate, ditrimethylolpropane tetrahydrophthalate tetra(meth)acrylate, tris(2-hydroxyethyl)in cyanurate tri(meth)acrylate, trimethylolpropane polyglycidyl ether tri(meth)acrylate,
Novolak type epoxy acrylic acid 1/-et and the like are preferred. Such polyfunctional oligomers preferably account for about 10 to 80% by weight of the total film-forming components.

Other film-forming components used together with the polyfunctional oligomers mentioned above have 1 to 2 functional groups.
Any conventionally known oligomers and polymers can be used.

The paint used in the present invention also includes a photopolymerization initiator, a solvent, and an extender pigment that imparts chicken-tropic properties to the paint.

As the photopolymerization initiator, any conventionally known initiators such as 2,2-dimethoxy-2-phenylacetophenone, 2-chlorothioxanthone, benzophenone, jetoxyacetophenone, benzoin isobutyl ether, and 2-methylthioxant 7 can be used.

The polymerization initiator L1 is used in an amount of about 1 to 6 parts by weight per 100 parts by weight of the film-forming component.

Solvents must be inert to other ingredients and are used to adjust the viscosity of the paint. For example, ethyl acetate, butyl acetate, methano-1-hethanol, inpropatol, toluene, xylene, methyl cellosolve, ethyl cellosolve, etc. are preferred, and are used in a proportion of about 10 to 200 parts by weight per 100 parts by weight of the film-forming component. It is preferable to use

Extender pigments are substances that suppress the permeability of paints into paper, such as aerosil, clay, talc, calcium carbonate, precipitated barium sulfate, white carbon, butyl white, etc., which add chicken-tropic properties to paints. Approximately 1 to 1% per 100 parts by weight of the film-forming component is preferably applied.
It is used in a proportion of 15 parts by weight.

The coating material used in the present invention may contain other additives such as an antiblocking agent, an antistatic agent, a leveling agent, etc., as necessary.

In the method of the present invention, the reverse side of the coated paper as described above is coated with a gravure coater, a roll coater, and a strip coater. j,,,) The coating is applied using a coating means such as a reverse coater, dry offset coater, air knife coater, brush coater, spray coater, etc., so that the solid content of the coating material is at a ratio of about 1 to By/-. This coating amount can also be adjusted by increasing or decreasing the amount of solvent used.

After applying the paint, the solvent is removed by evaporation, and the paint is cured by irradiation with ultraviolet rays from a high-pressure mercury lamp or other arbitrary ultraviolet irradiation source. A few seconds to several tens of seconds is sufficient for the irradiation time, and the irradiation time can be adjusted by continuously moving the paper to be irradiated.

By doing the above, a very thin (approximately 0.5 to 5μ) coating film with a very high crosslinking density is formed on the back side of the coated paper, and as a result, the paper becomes thinner due to changes in humidity, etc. Curling is prevented.

Compared to the conventional method of preventing paper curl, the conventional method prevents paper from curling by approximately 10 to 20 tons/l? While acceptable curl prevention is possible with a coating film of approximately 1 to 8
F. The hawk coating can sufficiently prevent curling, and combined with its operating speed, it is very economical.

Next, the present invention will be specifically explained with reference to Examples.

The words ``dou'', ``chi'', or ``chi'' are based on double stars.

Example 1 A photocurable paint having the following composition was prepared.

A) Dipentaerythritol hexaacrylate
75 (parts) Neopentyl glycol diacrylate
5 Hydroxybutyl acrylate, 10 Tripropyle/Glycol diacrylate 102
．． 2-/methoxy 2-phenylacetophenone 5
2-dichlorothioxanthone 0.5 Aeroseal 5 Antiblocking agent 2 Ethyl acetate
70 toluene
30B) Tetraglycidyl ether acrylate 4゜trimethylolbutane triacrylate) 20 Polyethylene glycol diacrylate) 15 Dipentaerythritol hexaacrylate 10 Oligoester acrylate 10 Benzophenone
5 triethanolamine
3 clay
20 Aerosil
, 7 anti-blocking agent
ethyl acetate
70 toluene
30C) Silicone acrylate 45 Pentaerythritol tetraacrylate 25 Hydroxypivalic acid diacrylate 15 Hydroxybutyl acrylate 10 Cyphthylphenyl phosphate 3 Jetoxyacetophenone 2 Bensoyl inbutyl ether 3 Talc 10 Aeroseal 5 Antiblocking agent 2 Ethyl acetate 70 Toluene
30D) Oligoester acrylate 25 dipentaerythritol hexaacrylate 30 melamine acrylate 15 bisphenol siglycidyl ether acrylate 15 neopentyl glycol diacrylate 5 benzophenone 52-methylthioxanthone 1 triethanolamine 2 calcium carbonate 20 Aerosil
5 Anti-blocking agent 2 Ethyl acetate
70 toluene
30E) Fatty acid modified epoxy acrylate 40 Dipentaerythritol hexaacrylate 20 Polyethylene glycol diacrylate 152-Hydroxyisoglobyl acrylate 15 Benzophenone
5 triethanolamine
3 Aerosil
5 Precipitated barium sulfate
20 Anti-blocking agent
2Ethyl acetate 7
0 toluene 30
Example 2 Paper curl prevention was carried out under the conditions shown in Table 1 below.

Claims (1)

[Claims] A photocurable paint containing a monomer and/or oligomer having 93 or more functional groups per molecule is applied to the other side of paper that has been coated on one side, and then cured. How to prevent paper from curling.