JPH0781113B2 - Coating agent consisting of silicone-based graft copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the Invention (Industrial field of application) The present invention exhibits the properties of silicone such as lubricity, releasability, water repellency, heat resistance, and the like. The present invention relates to a coating agent having excellent adhesion to a coated material.

The silicone in the present invention is a linear organopolysiloxane.

[Conventional Technology and its Problems] Various silicone-based coating agents have been developed as coating agents for imparting properties such as lubricity, releasability, water repellency, and heat resistance to the surface of a substrate. Specifically, silicone alkyd varnish, silicone epoxy varnish,
Silicone acrylic varnish, silicone polyester varnish, silicone urethane varnish and the like are known.

However, the above-mentioned silicone varnish does not have sufficient adhesion to the object to be coated, and when it is applied to a plastic such as polyethylene terephthalate, for example, a primer is currently used to improve the adhesion.
Further, in the above-mentioned silicone varnish, the one in which the content ratio of silicone is reduced for the purpose of improving the adhesiveness has a problem that lubricity and releasability are inferior. It has been extremely difficult to improve the adhesiveness and coating strength as well as the lubricity and releasability.

As a means for solving the above-mentioned problems, a coating agent of a graft copolymer system using silicone as a branch component and an alkyl acrylate copolymer as a trunk component has been proposed.
(JP-A-60-123518, JP-A-63-227670). Since the above-mentioned coating agent is mainly composed of a trunk polymer having adhesiveness to an object to be coated and a silicone-based graft copolymer composed of a silicone branch polymer, physical properties and lubricity related to adhesiveness and coating strength and Both physical properties related to releasability can coexist, and expectations are rising for applications such as weather resistant paints, surface protection materials for various plastic films and molded products.

However, the coating agent containing the above silicone-based graft copolymer as a main component has a problem due to bleeding of ungrafted silicone contained in a small amount in the graft copolymer onto the surface of the coating film. When the back surface of the film is coated as an anti-stick agent, the silicone bleeding during handling with a roll contaminates the surface of the film, and it is difficult to uniformly form an ink layer on the surface, and thus the application is limited. It was the current situation.

(B) Structure of the Invention [Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive studies for solving the above problems.

That is, the present invention is a radical polymerizable monomer having a linear silicone molecule having at least one terminal (meth) acryloyl group, a number average molecular weight of 3,500 to 50,000 macromonomer, and isobornyl (meth) acrylate as a main component. The number average molecular weight obtained by copolymerizing
A coating agent composed of a silicone-based graft copolymer having a melt flow index (hereinafter, abbreviated as MI) of 0.5 to 100 (g / 10 minutes) at 20,000 at 20,000.

In the present invention, the (meth) acrylic acid ester of isoborneol, that is, isobornyl (meth) acrylate, is used as the monomer for forming the trunk polymer of the graft copolymer, whereby unpolymerized silicone, that is, non-grafted silicone The amount could be greatly reduced and the heat resistance could be improved. The reason for this is not clear, but isobornyl (meth)
Since the acrylate polymer and silicone are excellent in compatibility, the silicone having a radical polymerizable group at the end of the molecule is easily brought close to the end of the growing chain of the polymer formed by isobornyl (meth) acrylate, resulting in It is speculated that the copolymerization rate of the silicone was increased.

Hereinafter, the present invention will be described in more detail.

[Macromonomer] As described above, the macromonomer in the present invention is a macromonomer having at least one terminal (meth) acryloyl group of a linear silicone molecule and having a number average molecular weight of 3,500 to 50,000, preferably 10,000 to 30,000. It is a macromonomer. A methacryloyl group is more preferable as the terminal polymerizable group of the macromonomer.

As described above, the macromonomer used in the present invention has a (meth) acryloyl group at at least one end of the linear silicone molecule, and the macromonomer has a (meth) acryloyl group at both ends of the linear silicone molecule. It may contain a macromonomer having a group. Generally, when a monomer having a plurality of radically polymerizable groups in one molecule is subjected to radical polymerization, a polymer capable of undergoing a crosslinking reaction is insolubilized, but a bifunctional monomer having a relatively large molecular weight is There is a fact that only the polymerizable group of is involved in the polymerization and the other is likely to remain unreacted, and as a result, the above-mentioned cross-linking reaction is unlikely to occur (for example, Proceedings of the Polymer Society, Vol. 31, No. 2, p. 147 ( 1982)]. In the present invention, a macromonomer having a number average molecular weight of 3,500 to 50,000 is used, and as a result, even if a monomer mixture containing a macromonomer having a (meth) acryloyl group at both ends of the molecule is radically polymerized. A cross-linking reaction hardly occurs and a polymer which can be suitably used as a coating agent is obtained.

When the number average molecular weight of the macromonomer is less than 3,500,
Properties derived from silicone, that is, properties such as lubricity and releasability are not expressed, and such a low molecular weight macromonomer contains a macromonomer having a (meth) acryloyl group at both ends of the molecule, The crosslinking reaction in radical polymerization becomes remarkable, and the polymer cannot be suitable as a coating agent. On the other hand, when the number average molecular weight of the macromonomer exceeds 50,000, the polymerizability of the macromonomer is poor and unpolymerized silicone remains.

As the silicone serving as the skeleton of the macromonomer, a linear dialkyl polysiloxane represented by a linear dimethyl polysiloxane or the like is preferable, as shown in Examples described later.

The number average molecular weight in the present invention is a polystyrene equivalent number average molecular weight determined by gel permeation chromatography.

The macromonomer can be produced by the method shown below. For example, as a production method utilizing an anionic polymerization method, a polymerization initiator such as lithium trialkylsilanolate is used to prepare a cyclic trisiloxane or a cyclic tetrasiloxane. Polymerize to obtain a silicone living polymer,
There is a production method of reacting this with γ-methacryloyloxypropylmonochlorodimethylsilane (for example, JP-A-59-78236), and as a production method utilizing a condensation reaction, JP-A-58-167606. And JP-A-60
The method of producing a macromonomer by the condensation reaction of a silicone having a silanol group at the terminal with γ-methacryloyloxypropyltrimethoxysilane and the like, which is disclosed in Japanese Patent Publication No. 123518, and the like.

A macromonomer produced by a method other than the above method can also be used. As another production method, a polyfunctional alkoxysilane (or silanol) and (meth) acryloxyalkylalkoxy described in JP-A-1-123814 can be used. Cyclic siloxanes described in “Methods for reacting silanes” and “Synthesis and applications of reactive polymers” (CMC, supervised by Takeshi Endo) and 1,3-bis (methacryloxypropyl)
Examples thereof include a method of producing tetramethyldisiloxane using trifluoromethanesulfonic acid as a catalyst.

[Silicone-based Graft Copolymer] The silicone-based graft copolymer of the present invention (hereinafter simply referred to as a graft copolymer) comprises the macromonomer and a radical-polymerizable monomer containing isobornyl (meth) acrylate as a main component. Obtained by radical copolymerization,
Structurally, it is a graft copolymer whose main component is a polymer having silicone as a branch component and isobornyl methacrylate monomer unit as a main component, and having a number average molecular weight of 25,000 to 30.
At 0,000, MI is 0.5-100 (g / 10 minutes).

When the number average molecular weight of the graft copolymer is less than 25,000, the mechanical strength of the coating film obtained when used as a coating agent is poor, while the graft copolymer having a molecular weight of more than 300,000 is adopted in the present invention. According to the present polymerization method, it is difficult to manufacture it.

The preferred amount of the branch component, ie, the silicone unit, in the graft copolymer is 2 to 60% by weight, and more preferably 5 to 50% by weight, based on the total amount of the units constituting the graft copolymer. If the amount of the silicone unit of the branch component is less than 2% by weight, the lubricity and releasability, which are the characteristics as a silicone-based coating agent, are not sufficiently expressed, while if it exceeds 60% by weight, the film-forming property is increased. And the phase separation easily occurs during polymerization in a solution system or during storage of the graft copolymer.

The preferred content of isobornyl (meth) acrylate in the radical-polymerizable monomer copolymerized with the macromonomer is 50% by weight or more based on the total amount of the radical-polymerizable monomer. When the amount of isobornyl (meth) acrylate is less than 50% by weight, the reduction of unpolymerized silicone in the obtained graft copolymer is not remarkable, and it is formed by the coating agent composed of the graft copolymer. Bleed of unpolymerized silicone occurs on the surface of the coating film.

The preferred glass transition temperature of the polymer forming the trunk component in the graft copolymer, that is, the trunk polymer, is 80 ° C or higher, and more preferably 100 ° C or higher. If the glass transition temperature of the trunk polymer is less than 80 ° C, the heat resistance of the graft copolymer is poor and the application is limited.For example, it is not used for the back coating agent of a thermal transfer film that comes into contact with a high temperature material. hard.

As the other radically polymerizable monomer that forms the trunk component together with isobornyl (meth) acrylate, a monomer having a homopolymer glass transition temperature of 20 ° C. or higher is preferable, and specifically acrylic acid, acrylic acid tert-butyl, 2,2-dimethylpropyl acrylate, cyclohexyl acrylate, 2-tert-butylphenyl acrylate, 2-naphthyl acrylate, 4-methoxyphenyl acrylate, 2-methoxycarbonylphenyl acrylate, acrylic acid 2
-Ethoxycarbonylphenyl, 2-chlorophenyl acrylate, 4-chlorophenyl acrylate, 2-cyanobenzyl acrylate, 4-cyanophenyl acrylate,
P-tolyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, methacrylic acid Benzyl acid, 2-dianoethyl methacrylate, 2-hydroxyethyl methacrylate, 3-oxabutyl methacrylate, γ-methacryloyloxypropyltrimethoxysilane, acrylamide, butylacrylamide,
N, N-dimethyl acrylamide, piperidyl acrylamide, methacrylamide, 4-carboxyphenyl methacrylamide, 4-methoxy carboxyphenyl methacrylamide, ethyl ethacrylate, methyl chloroacrylate, ethyl-α-chloroacrylate, propyl-α-chloroacrylate , Isopropyl-α-chloroacrylate, methyl-α-fluoroacrylate, butyl-α-butoxycarbonyl methacrylate, butyl-α-cyanoacrylate, methyl-α-phenyl acrylate, vinyl chloride, vinyl fluoride, 1,2-difluoroethylene , Chlorotrifluoroethylene, 1,2-dichloro-1,2-difluoroethylene, 3,3,3-tritrifluoropropylene, 2,3,3,3-tetrafluoropropylene, hexafluoropropylene, 2- Of ethyl ethylene, acrylonitrile, methacrylonitrile, vinyl acetate, styrene, methyl styrene, dimethyl styrene, butyl styrene, methoxystyrene, butoxystyrene,
Chlorostyrene, dichlorostyrene, bromostyrene,
Examples thereof include fluorostyrene, iodostyrene, carboxystyrene, dimethylaminostyrene, hydroxymethylstyrene, phenylstyrene, benzoylstyrene, α-methylstyrene, vinylpyridine and the like.

Next, a radical polymerization method for obtaining a graft copolymer will be described.

As the polymerization method, a radiation irradiation method using ultraviolet rays or electron beams or a method using a radical polymerization initiator can be used. The method is preferred,
It is more preferable to use a solution polymerization method in which the polymerization is carried out in an organic solvent.

The selection of the solvent to be used in the solution polymerization method is important, and preferred solvents include ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ethyl acetate, acetic ester solvents such as butyl acetate, benzene, toluene and xylene. Examples of the aromatic hydrocarbon solvent, cyclohexane, tetrahydrofuran, dimethylformamide, dimethylsulfoxide, hexamethylphosphoamide, and the like are preferable, and a ketone solvent, an acetic acid ester solvent, or an aromatic hydrocarbon solvent is more preferable.

When the above organic solvent is used, the amount of unpolymerized silicone is smaller than that when other organic solvents are used.

As the radical polymerization initiator, any of those used in general radical polymerization can be used, and for example, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxy ester and Examples thereof include organic polymerization initiators such as azobisisobutyronitrile, and inorganic radical polymerization initiators such as ammonium persulfate.

In the present invention, a relatively low polymerization temperature can be adopted, side reactions can be suppressed, and a graft copolymer having a clear structure can be obtained in high purity, and thus an organic peroxide or an azo compound having a low decomposition temperature is preferable. Azo compounds are particularly preferable.

Specific examples of the azo compound include azobisisobutyronitrile (hereinafter abbreviated as AIBN), azobis-4-cyanovaleric acid, azobis (2,4-dimethylvaleronitrile), azobis (4-methoxy-2,4). -Dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, azobis-1-cyclohexacarbonitrile and the like.

Generally, the temperature of radical copolymerization is preferably about 50 to 150 ° C, more preferably 60 to 100 ° C. The polymerization time is suitably 3 to 100 hours, preferably 5 to 10 hours.

The silicone-based coating agent of the present invention contains the above graft copolymer as an active ingredient, and for example, an organic solvent solution of the graft copolymer obtained by a solution polymerization method is
It can be used as a coating agent as it is or diluted with a solvent such as thinner. Similarly, an aqueous emulsion dispersion of a graft copolymer obtained by an emulsion polymerization method is used as a coating agent as it is or diluted with water or the like. Can be used.

When a cross-linked structure is to be introduced into the coating film to be formed, if the graft copolymer has a functional group such as a hydroxyl group, a polyvalent isocyanate compound or a melamine curing agent can be used in combination, and the graft copolymer can be made of silicon. If there is a hydrolyzable functional group bonded to an atom, dibutyltin dilaurate or the like can be crosslinked and cured by utilizing the reaction of the functional groups in the presence of a catalyst.

The coating agent of the present invention is a resin other than the above graft copolymer, for example, an acrylic resin, an epoxy resin,
Unsaturated polyester resin, fluorine resin
A curable composition comprising a radically polymerizable component as a polymer pre-driving substance such as polyester polyacrylate disclosed in JP-A-49-120889 may be blended. The amount of the resin other than the graft copolymer used is preferably 50% by weight or less based on the total amount of the graft copolymer and these resins.

Further, to the coating agent of the present invention, additives such as a filler, various stabilizers and pigments may be added, and specifically, various silicas, calcium carbonate, magnesium carbonate,
Examples thereof include additives such as titanium oxide, iron oxide, glass fiber, dispersion stabilizer, antioxidant, antistatic agent, and ultraviolet absorber.

Coating amount of the object to be coated of the coating agent of the present invention is suitably 0.01 to 10 g / m ² from the film formation of the relationship, more preferably from 0.05 to 1 g / m ^2.

[Subject] The silicone coating agent of the present invention can be coated on the surface of various materials such as rubber, plastic, metal, ceramics, glass, wood and paper.

Specifically, magnetic tapes / films, cassette sheets and backside coating agents for heat-sensitive transfer recording films; release papers, masking tapes, adhesive tapes, confectionary cups, concrete, molds for mortar and gypsum, stamping foils, etc. Agents and mold release agents for plastics and ceramics; Lubricating and protective coating agents for magnetic cards, IC cards, cash cards, credit cards, prepaid cards, magnetic tickets, etc .; Anti-graffiti paints, anti-sticking paints, antifouling paints Vehicles for paints, anti-icing / condensation prevention paints and high weather resistance paints; In addition to these, foaming agents for urethane foam, high weather resistance coating agents for resin impregnated wood, glazing leather, water repellent and antifouling coatings Agents and the like.

[Examples, Reference Examples and Comparative Examples] The present invention will be described more specifically with reference to Examples, Reference Examples and Comparative Examples below.

The physical properties of the silicone-based graft copolymer in each example and the coating film physical properties of the silicone-based coating agent obtained from the copolymer were evaluated by the methods described below. Further, parts and% represent parts by weight and% by weight, respectively.

a) Migration of unpolymerized silicone: A polyethylene terephthalate film (hereinafter referred to as PET film) coated with a coating agent on one side was used as a test object, and five of these films were stacked so that they were alternately in contact with each other. It was sandwiched between two glass plates and heated at 60 ° C. for 24 hours under a load of 40 g / cm ² . Then, the surface tension of the uncoated surface of the film was measured using a wetting index standard solution (manufactured by Wako Pure Chemical Industries, Ltd.) (JISK67
According to 68-1977).

The higher the measured surface tension number, the less bleed due to unpolymerized silicone.

b) Releasability: Using an object to be coated coated with a coating agent as a sample, KOKUYO cellophane tape (24 mm width) is pressure-bonded to the coating surface, and the cellophane tape is pulled by a tensile tester at a pulling speed of 200 mm / min, 25 ° C, It was evaluated by the tensile strength (g) when peeled 180 ° under the condition of 60% RH.

c) Lubricity: For the coated object coated with a coating agent, using a surface property measuring device manufactured by Shinto Chemical Co.,
The dynamic friction coefficient (μk) was measured under the following conditions.

Contact: Stainless steel ball with a diameter of 10 mm.

 Load: 50g Moving speed: 150mm / min.

 Temperature: 25 ℃, Humidity 60% RH.

Example 1 In a flask equipped with a stirrer, a condenser and a thermometer, α,
ω-dihydroxypolydimethyl silicone 111 g (0.005 mol), p-toluenesulfonic acid 0.12 g, toluene 74 g, methyl ethyl ketone (hereinafter referred to as MEK) 37 g, and γ-methacryloyloxypropyltrimethoxysilane 2.48 g (0.01 mol) were charged, and the mixture was heated at 70 ° C. for 3 hours. Heated. Then, after cooling to room temperature, a basic anion exchange resin (A-21 manufactured by Organo Corporation) was added to the reaction solution.
30 g was added and neutralized by stirring at 40 ° C. for 2 hours. The ion exchange resin was removed by filtration, and the filtrate was distilled under reduced pressure to obtain 110 g of a colorless transparent oily macromonomer. The number average molecular weight of the macromonomer was 35,000.

Next, in a flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen introducing tube, 70 parts of isobornyl methacrylate (Kyoeisha Oil and Fat Chemical Co., Ltd. light ester IB-X) per 30 parts of the above macromonomer, AIBN1.0 Parts and toluene 1
After charging 00 parts and maintaining the temperature at 80 ° C. for 4 hours while bubbling nitrogen, 0.5 part of AIBN was added and heated at the same temperature for 4 hours to synthesize a graft copolymer.

The graft copolymer solution was diluted with MEK to a solid content of 10%, and the obtained coating agent was used to coat a PET film having a thickness of 6 μm with a bar coater, followed by heating and drying at 70 ° C. for 10 seconds to obtain a film thickness. A 0.5μ coating was applied.

The results of evaluating the physical properties of the formed coating film are as follows.

 Lubricity: 0.036 μk, migration of unpolymerized silicone: 38 dyne / cm, mold release property: 28 g / inch.

Example 2 A graft copolymer was synthesized in the same manner as in Example 1 except that FM0725 (produced by anionic polymerization method, molecular weight 10,000) manufactured by Chisso Corporation was used as the macromonomer. A coating film for evaluation of physical properties was formed by the method of 1. and the following results were obtained.

 Lubricity: 0.031 μk, Migration of unpolymerized silicone: 38 dyne / cm, Release property: 25 g / inch.

Example 3 All the same operations as in Example 1 except that 100 parts of MEK was used as the polymerization solvent and 30 parts of the macromonomer used in Example 1, 60 parts of isobornyl methacrylate and 10 parts of methacrylic acid were used as the monomer components. Thus, a graft copolymer solution was obtained.

Using the obtained graft copolymer solution, a coating film for evaluating physical properties was formed in the same manner as in Example 1, and the following results were obtained.

 Lubricity: 0.043 μk, migration of unpolymerized silicone: 38.5 dyne / cm, releasability: 32 g / inch.

In addition, analytical data for immobilization was collected on the graft copolymer itself separated by evaporating the solvent from the above graft copolymer solution.

MI at 270 ° C was 19.0 (g / 10 min), elemental analysis results are shown below, and infrared absorption spectrum was 1st
It was as shown in the figure. C58.5%, H9.3%, Si11.1%, O21.1
% (Si was obtained by converting the ignition residue to SiO ₂ and converting it to Si.) Example 4 100 parts of MEK was used as a polymerization solvent, and 30 parts of the macromonomer used in Example 1 was used as a monomer component. A graft copolymer solution was obtained in the same manner as in Example 1, except that 40 parts of isobornyl methacrylate and 30 parts of methyl methacrylate (hereinafter referred to as MMA) were used.

Using the obtained graft copolymer solution, a coating film for evaluating physical properties was formed in the same manner as in Example 1, and the following results were obtained.

 Lubricity: 0.032 μk, migration of unpolymerized silicone: 38 dyne / cm, mold release: 39 g / inch.

Example 5 Using 100 parts of the graft copolymer solution obtained in Example 3 and diluting it with MEK to a solid content of 15%, a solution obtained by adding a polyvalent isocyanate compound, Coronate EH (Japan Polyurethane )) Was added.

A coating film was formed from the above solution and its physical properties were evaluated, and the following results were obtained.

 Lubricity: 0.040 μk, migration of unpolymerized silicone: 38 dyne / cm, mold release property: 30 g / inch.

Example 6 A graft copolymer solution was obtained in the same manner as in Example 1, except that 5 parts of the macromonomer synthesized in Example 1, 85 parts of isobornyl methacrylate and 10 parts of methacrylic acid were used as the monomer components.

A coating film was formed from the obtained graft copolymer solution and its physical properties were evaluated. The results are as follows.

 Lubricity: 0.260 μk, migration of unpolymerized silicone: 40 dyne / cm, mold release: 100 g / inch.

Comparative Example 1 In place of 70 parts of isobornyl methacrylate used in the production of the graft copolymer in Example 1, 60 parts of MMA and 10 parts of methacrylic acid were used as a monomer for the trunk polymer, and all were carried out. A coating was obtained and a coating film was prepared in the same manner as in Example 1. The physical properties of the coating film were as follows.

 Lubricity: 0.038 μk, migration of unpolymerized silicone: 31 dyne / cm, releasability: 30 g / inch.

Comparative Example 2 100 parts of the graft copolymer solution obtained in Comparative Example 1 was mixed with MEK.
Coronate EH6.5 to a solution diluted to 15% solids with
Added parts.

Thereafter, a coating film was formed in the same manner as in Example 1 and an evaluation test was conducted. The results are as follows.

 Lubricity: 0.035 μk, migration of unpolymerized silicone: 31 dyne / cm, mold release property: 25 g / inch.

From each of the above examples, in a comparative example using a conventional silicone-based graft polymer that does not use isobornyl methacrylate as a monomer for forming the trunk polymer, the surface tension of the coating film after heat treatment is 30 to 31 dyne. / cm, the migration of unpolymerized silicone is quite remarkable, whereas according to the examples of the present invention, the surface tension of the coating film after the same treatment is 38 dyne / cm or more, It is clear that the silicone migration is extremely low.

(C) Effect of the Invention The silicone-based graft copolymer of the present invention obtained by using isobornyl (meth) acrylate as a monomer for forming a trunk polymer is a trace amount of unpolymerized silicone as is clear from the specific examples. It only contains.

Therefore, the coating agent composed of the copolymer forms a coating film having excellent adhesion to an object to be coated, and excellent lubricity, releasability and water repellency, and less bleeding of unpolymerized silicone. Starting with the backside coating agent of thermal transfer recording film, release coating agent of release paper for adhesive tape,
It can be suitably used for various applications such as a lubricating coating agent for magnetic tapes and IC cards.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum of the graft copolymer produced in Example 3.

Claims (1)

[Claims] 1. A linear silicone molecule having at least one terminal (meth) acryloyl group and having a number average molecular weight of 3,50.
0-50,000 macromonomers and isobornyl (meth)
Obtained by copolymerizing a radically polymerizable monomer containing acrylate as a main component, the number average molecular weight is 25,000 to 300,000.
And the melt flow index at 270 ° C is 0.5-10.
Coating agent consisting of 0 (g / 10 minutes) silicone-based graft copolymer.