JPH05311131A - Release agent for application to back surface - Google Patents

Abstract

PURPOSE:To provide the aqueous release agent for application to the back surface of an adhesive tape, containing a copolymer emulsion prepared by polymerizing a silicone macromonomer-containing O/W type emulsion and capable of controlling the peel resistance value. CONSTITUTION:This release agent for application to the back surface contains a copolymer emulsion synthesized by free radical polymerization of an O/W type emulsion essentially composed of (A) 5 to 60wt.% compound of formula I [R is OH, Ph or formula II to VII (Ph is phenyl or an alkyl-substituted phenyl; m is 0 to 10); R1 is formula V to VII; R2 is OH or formula IV to VII; x, y and z are each 0 to 150 and satisfy x+y+z=10 to 150] and (B) 95 to 40wt.% unsaturated compound (e.g. styrene or an acrylic acid ester) copolymerizable therewith and having <=0.5mum particle diameter. The copolymer emulsion contains unreacted (A) in an amount of <=5wt.% [prepared by using a silicone monomer having a molecular weight lower than that of (A) in an amount of 1 to 80wt.% based on the total. amount of the used silicone] based on the total amount of the used silicones and exhibits >=15 deg.C the lowest film-forming temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release agent for the back surface treatment of adhesive tapes used in a wide range of fields such as medical, office, construction and painting.

[0002]

2. Description of the Related Art Adhesive tapes are used in a wide range of fields due to their convenience of use. Has been processed. That is, the release agent is applied to the back surface of the tape to give its releasability.
Most of the releasing treatment is carried out by applying an organic solvent solution of a silicone resin, drying it, and then thermally curing or adding a curing agent to crosslink the silicone resin. Other than silicone resin, shellac is used, but this is also used as an organic solvent solution such as alcohol.

Further, with these conventional solvent-based silicone resin release agents, it is difficult to control an area having a large peel resistance value necessary for laminating tapes, and it is not possible to easily manufacture an adhesive tape having an appropriate peel resistance value. is there. That is, since the conventional silicone resin-based release agent has a very small peel resistance value even if it is applied in a very small amount, it is actually very difficult to gradually change the resistance value from a middle value to a high value. Difficult and its control is almost impossible.

In addition, in the case of the conventional organic solvent type silicone resin release agent, the silicone resin needs to be added with a catalyst such as platinum and cured by addition or condensation reaction by heating, which makes operation and handling complicated and difficult in practical use. Not only is there
It is inevitable that problems such as a decrease in adhesive strength due to transfer of uncrosslinked components in the silicone resin to the pressure-sensitive adhesive layer are unavoidable.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a release agent for back surface treatment of water system, keeps working environment clean, and eliminates pollution caused by volatilization of solvent into the atmosphere.

In addition, the present invention overcomes the problems of conventional organic solvent type silicone resin type releasing agents such as difficulty in controlling the peeling resistance value and incomplete curing reaction due to addition reaction or condensation reaction in the silicone resin. Therefore, an object of the present invention is to develop a release agent for back surface treatment, which solves the trouble of the decrease in adhesive strength due to the transfer of the uncrosslinked silicone resin component to the adhesive layer.

Further, according to the present invention, a barrier coating for sealing is not required by a polyethylene laminating process or a polyvinyl alcohol aqueous solution, which is required in the case of a conventional solvent type silicone resin release agent, and a silicone resin crosslinking treatment is not required. It is also an object to provide a release agent for backside treatment at a low cost, which is extremely industrially advantageous.

[0008]

The present invention has the general formula (I)
Compound represented by

[Chemical 2] 5-60 wt% and unsaturated compounds copolymerizable therewith
The unreacted content of the silicon macromonomer obtained by free-radical polymerization of an O / W emulsion having a particle size of 0.5 μm or less containing 95 to 40% by weight as an essential component is 5% by weight or less (based on the total amount of silicon used). The above-mentioned problems were solved by developing a release agent for backside treatment, which comprises a copolymer emulsion having a minimum film forming temperature (MFT) of 15 ° C or higher.

In this case, when the content of the silicon macromonomer represented by the general formula (I) is less than 5% by weight, the peeling resistance is not sufficiently lowered and the base material frequently breaks. When it is more than%, the polymerization of the macromonomer component is difficult to proceed, and a considerable amount of unreacted component remains, which causes the transfer of the silicon component to the pressure-sensitive adhesive layer, which causes a decrease in the tackiness. Also, a copolymer emulsion is not preferable because the film forming property is poor.

In an O / W type emulsion containing a silicon macromonomer and an unsaturated compound copolymerizable therewith as an essential component, the particle size thereof should be 0.5 μm or less. If it is larger than 0.5 μm, polymer fine particles containing no silicon macromonomer are generated, and the polymer containing a large amount of macromonomer component tends to become coarse particles, that is, agglomerates. Is not effective, and the obtained emulsion of the copolymer is inferior in film-forming property and is not preferable.

In the preparation of an O / W type emulsion containing a mixture of the above unsaturated compound and a silicon macromonomer as an essential component and having a particle size of 0.5 μm or less, the mixture and an emulsifier aqueous solution are emulsified by a powerful emulsifying device. By doing.

In order to reduce the particle diameter to a predetermined value of 0.5 μm or less, the emulsifier, the powerful emulsifying device and the emulsifying operation conditions must be appropriately selected. If the selection is inappropriate, the particle size will not be 0.5 μm or less, and even if a uniform emulsion is formed, it will change over time and phase separation will occur.

As the emulsifier, all emulsifiers used in ordinary emulsion polymerization can be used, and lauryl alcohol,
Higher alcohols such as cetyl alcohol are also considered as auxiliary emulsifiers. Of course, so-called copolymerization type emulsifiers having a radical-polymerizable unsaturated bond are also included in the object, and it is preferable to use this.

The powerful emulsifying machine may be a rotor and a stator, a high-speed rotating part, an ultrasonic type, a high-pressure type that passes through pores, and the like. Wide application range and convenient.

The unreacted content of silicon macromonomer in the copolymer emulsion of the present invention must be 5% by weight or less (based on the total amount of silicon used). Preferably 2% by weight
It is below. If this is not the case, transfer of unreacted residual silicon macromonomer to the adhesive layer occurs,
It causes troubles such as decrease in tackiness.

As one means for controlling the unreacted content of the silicon macromonomer to be 5% by weight or less (based on the total amount of silicon used), it is effective to use a silicon monomer having a lower molecular weight than that of the silicon macromonomer. is there. That is, there is almost no compatibility between the high molecular weight silicon macromonomer and the unsaturated compound copolymerized therewith,
Extremely speaking, it is like oil and water, and its copolymerizability is very poor.
It is relatively difficult to reduce the amount to about wt% (total amount of silicon used). In order to improve the compatibility in addition to establishing optimum polymerization conditions, the present invention is to combine a silicon macromonomer with a silicon monomer having a molecular weight lower than that of the silicon macromonomer to obtain unreacted silicon macromonomer. It was found to be effective in suppressing unreacted components. However, it is not preferable to use the low molecular weight silicon monomer alone because it is difficult for the produced copolymer emulsion to exhibit various excellent characteristics of the silicon macromonomer. The amount of low molecular weight silicon monomer used is 1 to 80% by weight based on the total amount of silicon macromonomer used.
Is. If it is less than 1% by weight, no effect can be seen in suppressing unreacted silicon macromonomer. On the other hand, if it exceeds 80% by weight, the original silicon characteristics are lost.

The silicon monomer having a molecular weight lower than that of the silicon macromonomer used together with the silicon macromonomer is less than x + y + z = 10 in the general formula (I), and as a commercial product, KBM-503 (manufactured by Chisso Corporation) is used. ), Sila Ace S710 (Chisso Corporation)
Manufactured by Chisso Co., Ltd.) and the like.

On the other hand, the silicon macromonomer in the general formula (I) is x + y + z = 10 or more, preferably x +.
y + z = 10 to 150, and F is a commercially available product.
M-0725, FM-0711, FM-2231 (above, Chisso Corporation make) etc. are mentioned.

The MFT of the resulting copolymer emulsion must be above 15 ° C. If it is lower than that, peeling resistance becomes large and the adhesive tape substrate is damaged. This includes the glass transition temperature (T) of the unsaturated compound that can be copolymerized with the silicon macromonomer.
g) easily obtained by adjustment.

Examples of the unsaturated compound which can be copolymerized with the silicon macromonomer include vinyl esters such as acrylic acid ester, methacrylic acid ester, styrene, vinyl acetate, vinyl propionate and vinyl versatate, ethylene, butadiene, isoprene and chloride. vinyl,
Not only neutral ones such as vinylidene chloride but also acrylic acid,
Methacrylic acid, itaconic acid, maleic acid, fumaric acid,
Acidic compounds such as vinyl sulfonic acid, phosphoric acid esters of hydroxyethyl acrylate or methacrylate,
Further, vinyl pyridine, vinyl imidazole, dimethylaminoethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methacrylonitrile and a quaternary compound thereof can be used. In short, all unsaturated compounds that directly or indirectly copolymerize with the silicon macromonomer are targeted.

The polymerization catalyst may be any azo compound such as azobisisobutyl nitrile or a peroxide such as benzoyl peroxide or persulfate, which is used as an initiator of radical polymerization, and may be either oil-soluble or water-soluble. However, in the former case, it is convenient to dissolve the silicone macromonomer in advance in a mixed liquid of an unsaturated compound copolymerizable therewith.

The polymerization reaction is carried out by bringing an O / W emulsion containing a mixture of the silicon macromonomer obtained as described above and an unsaturated compound copolymerizable therewith as an essential component to a predetermined temperature. In order to facilitate control of the reaction temperature, a part of the O / W emulsion is usually charged in a polymerization reactor and the rest is added at any time.

The copolymer emulsion-containing release agent thus obtained is applied to the back surface of an adhesive tape base material to which an adhesive is applied, and the back surface of the base material is treated with a release tape base material by drying. To be done. The coating thickness varies depending on the material of the pressure-sensitive adhesive, the property of the pressure-sensitive adhesive, the coating amount thereof, and the silicon content in the copolymer, but an average of 0.5 g / m ² or more is sufficient. In general, if it exceeds a certain value, the peeling performance does not change even if the coating thickness is increased.

[0024]

When the copolymer emulsion of the present invention is applied to an adhesive tape substrate and dried, a polydimethylsiloxane chain derived from a silicon macromonomer component forms a film localized on the air side to form an adhesive tape substrate. Is considered to cover. However, since the polydimethylsiloxane chain is incorporated as part of the high molecular weight copolymer by radical polymerization reaction, the solvent-based low molecular weight silicon compound is heated to crosslink to a high molecular weight, and the back surface of the adhesive tape substrate It is considered that they have the same effect as the conventional mold release agent that gives the mold release property to.

Further, the release agent of the present invention can easily and finely control the peeling resistance by changing the amount of the silicon macromonomer component used in the copolymer emulsion. This is because the peel resistance changes more gently with respect to the coating amount (that is, the silicon coating amount) than in the conventional method (FIG. 1,
See FIG. 2).

Further, in the present invention, as long as the unreacted content of the silicon macromonomer of the copolymer emulsion is maintained at 5% by weight (based on the total amount of silicon used) or less, the trouble caused by the transfer of the silicon component to the adhesive layer is caused. Can be prevented. This was the current situation that in the conventional method of lowering the unreacted component to a certain value or less in the conventional method in which a low-molecular-weight silane and a siline coat compound are made to have a high molecular weight by curing and crosslinking, the above-mentioned in the present invention. As described above, by using the low molecular weight silicon monomer in combination and selecting the polymerization conditions, it is more easily achieved that the unreacted content of the silicon macromonomer is 5% by weight or less with respect to the amount used.

In the present invention, the molecular weight and content of the silicon macromonomer, MFT of the resulting copolymer emulsion,
By changing many factors such as the coating amount, the release agent for backside treatment with the same performance as the conventional organic solvent type silicon compound will be provided in a safe and environmentally friendly form because it is an aqueous type, and its effect is indeed It is considered large.

[0028]

EXAMPLES The present invention will be illustrated by the following examples. (Example 1) 25 parts by weight of a silicon macromonomer (FM-0725, manufactured by Chisso Corporation) as a silicon component, 5 parts by weight of a low molecular weight silicon monomer (FM-0705, manufactured by Chisso Corporation), and copolymerizable therewith. As unsaturated compounds, 10 parts by weight of methyl acrylate, 15 parts by weight of 2-ethylhexyl acrylate, 41 parts by weight of styrene, 2
-0.2 parts by weight of azobisisobutyronitrile as a polymerization catalyst was added to and dissolved in a mixture of 2 parts by weight of hydroxyethyl methacrylate and methacrylic acid, and water was added to the mixture to prepare a 38% by weight solution. As an emulsifier, anionic and copolymerizable Eleminol JS-2 (1
0 wt% aqueous solution, Sanyo Kasei Co., Ltd. 0.3 wt% (to emulsion) and polyoxyethylene nonylphenol ether (Emulgen 920, Kao Co. Ltd.) 0.6
% By weight was added to the above-mentioned monomer-water mixture, and high-speed emulsification was performed using a high-pressure homogenizer (Manton-Gaulin) to obtain an O / W type emulsion having an average particle diameter of 0.26 μm. The polymerization reaction was carried out using the emulsion dropping method under the following conditions. Nitrogen substitution 30 minutes Precharge 5% by weight of monomer emulsion Reaction temperature 80 ° C. ± 1 ° C. Dropping time of monomer emulsion 4 hours Aging time 2 hours The properties of the obtained copolymer emulsion were as follows. Solid content concentration 37.8% by weight Particle size (average value) 0.18 μm pH 9.0 Viscosity (30 ° C.) 10 cps Unreacted silicon macromonomer 5% by weight (total amount of silicon used) Silicon macromonomer component content 30% % (Based on solid content of copolymer) MFT 40 ° C.

(Examples 2 to 6) The amount and type of silicon macromonomer used in Example 1 and the amount of unsaturated compound copolymerizable therewith were changed as shown in Table 1, and Examples 2 to 6 were carried out. did. The obtained results are also shown in Table 1.

(Comparative Examples 1 to 4) The amount of macromonomer used in Example 1, the type and the amount of unsaturated compound copolymerizable therewith were changed as shown in Table 1, and Comparative Examples 1 to 4 were used.
The results obtained are also shown in Table 1. However, in Comparative Example 2, a homomixer was used instead of the high-pressure homogenizer (Manton-Gaulin), and the particle size of the O / W emulsion of the unsaturated compound containing the macromonomer was 3 to 4.
μm.

Example 7 Fine Xerox paper (60 g /
m ² ) and Japanese paper (Kamoi Koshigami Co., Ltd.) with 2 of the copolymer emulsions obtained in Examples 1 to 6 and Comparative Examples 1 to 4.
It was applied with a mil applicator and dried at 60 ° C. for 3 minutes to prepare a test sample. Based on JIS Z-0237, the above-mentioned test sample was used as a Washi tape (Kamoi Paper Co.
Peeling resistance value when pressure-bonded to a cellophane tape (manufactured by Nichiban Co., Ltd.) and a cellophane tape (manufactured by Nichiban Co., Ltd.). The applicator was changed from 2 mil to 1 mil, 3 mil, 4 mil, and 8 mil, and coating was performed to measure the peeling resistance value. As a result, there was almost no change as shown in FIGS. 3 and 4.

[0032]

[Table 1] MMA; methyl methacrylate 2EHA; 2-ethylhexyl acrylate St; styrene 2HEMA; 2-hydroxyethyl methacrylate MAA; methacrylic acid FM-0725; x + y + z = 131 FM-0711; x + y + z = 13 FM-2231; x + y + z = 131 1) FM-0705. (Manufactured by Chisso Corporation): x + y + z =
7 2) Total amount of silicone used 3) Solid content of copolymer 4) Peel resistance of Washi tape itself (backside treated with organic solvent-based silicon compound solution) 5) Peel tape itself (organic solvent) Backside treated with a system-based shellac solution) * Fogging of tape

[0033]

As shown in Table 1, the copolymer emulsion of the present invention obtained by using the silicon macromonomer component is a water-based product, but is a conventional organic solvent solution type back-treatment release agent. It was demonstrated that a back treatment release effect equal to or higher than that obtained by using the same was given.

In the conventional organic solvent solution type, the peel resistance value of the present Japanese paper tape is too small as shown by the horizontal broken line in FIG. 1, and it is technically possible to answer it though it is desired to make it a little larger. The reality is that it is difficult. It is clear from FIG. 1 that the use of the product of the present invention allows easy control. That is, the present invention has an advantage that it can cover an area where the prior art cannot. From the fact that it is a water-based product, there is no concern about environmental pollution due to solvent volatilization, health hazards for workers, risk of fire, etc., and from the viewpoint of resource saving and also from the viewpoint of extremely easy handling, the product of the present invention is Its use is highly expected.

[Brief description of drawings]

FIG. 1 shows the relationship between the silicone macromonomer content and the adhesive strength when a peeling resistance was measured by pressing a Camoy tape onto a test sample using Xerox paper in Example 7.

FIG. 2 shows the relationship between the silicon macromonomer content and the adhesive strength when the camoy tape in FIG. 1 is changed to cellophane tape.

FIG. 3 shows changes in adhesive strength when Xerox paper was used when the coating amount of the copolymer emulsion was changed.

FIG. 4 shows a change in adhesive strength when Japanese paper is used instead of Xerox paper as the base material in FIG.

Claims (2)

[Claims] 1. A compound represented by the general formula (I) (hereinafter,
It is called silicon macromonomer. ) [Chemical 1] 5-60 wt% and unsaturated compounds copolymerizable therewith
The unreacted content of the silicon macromonomer obtained by free-radical polymerization of an O / W emulsion having a particle size of 0.5 μm or less containing 95 to 40% by weight as an essential component is 5% by weight (based on the total amount of silicon used). ) Or less and a copolymer emulsion having a minimum film forming temperature (MFT) of 15 ° C. or more, a release agent for back surface treatment. 2. The release agent for backside treatment according to claim 1, wherein the silicon macromonomer contains a silicon monomer having a molecular weight lower than that of the silicon monomer in an amount of 1 to 80% of the total amount of silicon used.