JPS59227967A - Solventless pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide the titled adhesive compsn. having excellent melt coating characteristics and tackiness, by polymerizing alpha,beta-unsaturated compds. in the presence of a surfactant. CONSTITUTION:Polymerizable alpha,beta-unsaturated compds. (e.g. a mixture of a principal monomer such as ethyl acrylate, a functional monomer such as acrylic acid, and a modifying monomer such as styrene) are polymerized in the presence of a polymn. initiator and 0.1-40pts.wt. (per 100pts.wt. of the resulting solventless pressure-sensitive adhesive) surfactant (any of anionic, nonionic and cationic surfactant may be used) at 0-200 deg.C for 1-24hr to obtain an adhesive compsn. The surfactant may be used together with a resin (e.g. rosin, cumarone resin or an ethylene/vinyl acetate copolymer) which is solid at room temp. and can be liquefied by heating in place of the surfactant alone.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solvent-free pressure sensitive adhesive composition. More specifically, the present invention relates to a solvent-free pressure-sensitive adhesive composition that can be manufactured using an industrially advantageous manufacturing method and has excellent adhesive properties and coating suitability.

Solvent-free pressure-sensitive adhesives (also called hot-melt pressure-sensitive adhesives, also called adhesives) have already been developed using ethylene-vinyl acetate copolymers, styrene-butadiene, and styrene-isoprene block copolymers. There have been reports of materials mainly composed of thermoplastic polymers such as polymers.

However, for example, ethylene-vinyl acetate copolymers have limited durability, while styrene-butadiene and styrene-isoprene block copolymers have double bonds in their main chains that make them resistant to weathering. Due to issues such as gender issues, we are still unable to obtain products that are sufficient to meet market demands.

In order to solve these problems with conventional solvent-free pressure-sensitive adhesives, we have developed a solvent-free version of acrylic pressure-sensitive adhesives, which have already proven their usefulness as solvent- and emulsion-type pressure-sensitive adhesives. It has been long awaited. However, although there have been some reports in recent years regarding the development and research of acrylic solvent-free pressure-sensitive adhesives, not only have they not yet obtained anything that satisfies excellent adhesive properties and melt coating suitability. Despite research on its production method, no industrially effective method has been found.

In other words, an example of a method for obtaining an acrylic solvent-free pressure-sensitive adhesive is emulsion polymerization, but this method requires many steps and incidental work such as wastewater treatment when salting out to obtain a polymer. This is extremely inefficient. In addition, in the method of directly obtaining a solvent-free pressure-sensitive adhesive by bulk polymerization, it is difficult to control the polymerization heat generated during polymerization, so it is too dangerous to be adopted as an industrial manufacturing method. It is also difficult to adjust the molecular weight and molecular weight distribution of the polymer to suit the purpose.

The problem with the method of obtaining a solvent-free polymer by distilling off the solvent after solution polymerization is that it is easy to control the polymerization, but it takes a long time to distill off the solvent and is virtually useless. It is extremely difficult to remove the solvent to the extent that it becomes a solvent.

As a result of continuing research in view of the above circumstances, the present inventors have discovered that the present inventors have found that this material can be used in the presence of a surfactant, or in the coexistence of a surfactant and a resin that is solid at room temperature and can be melted and liquefied by heating. By using this as a polymerization medium (conceptually equivalent to a solvent in general solution polymerization) and polymerizing a polymerizable α, β-unsaturated compound in this medium,
It is now possible to control the sudden generation of polymerization heat as in the case of bulk polymerization, and from the standpoint of polymerization operations, it is possible to safely and efficiently apply the solution polymerization method that has been widely used in practice. It is possible to produce a polymer with a freely adjusted molecular weight and molecular weight distribution, and the surfactant used in the process and the resin that is solid at room temperature and can be liquefied by heating and melting can be obtained. The present invention was completed based on the discovery of multiple effects that effectively act on improving the melt coating suitability and adhesive properties of solvent-free pressure-sensitive adhesives.

That is, the present invention provides a combination of a resin (hereinafter referred to as resin (6)) that is solid at room temperature and can be liquefied by heating and melting with the surfactant (5) or in the presence of the surfactant (5). The object of the present invention is to provide a solvent-free pressure-sensitive adhesive composition obtained by polymerizing a polymerizable α,β-unsaturated compound (Q).

Regarding the surfactant (5) used in the present invention, as explained above, a polymerizable α,β-unsaturated compound (as long as it exhibits a medium effect as a polymerization site during the polymerization of Q) can be used. Anionic, nonionic, or cationic surfactants can be appropriately selected and used alone or in the form of a mixture without any limitation.

Examples of anionic surfactants include soaps, sulfate ester salts, sulfonate salts, phosphate ester salts, and the like. Examples of nonionic surfactants include polyethylene (or propylene) glycol type obtained from ethylene oxide and propylene oxide adducts, polyhydric alcohol type, and the like. Further, examples of the cationic surfactant include amine salt type and quaternary ammonium salt type. Amphoteric surfactants can also be used if desired.

The amount of surfactant (6) used differs depending on whether the surfactant is used alone or in combination with resin (6). It is desirable to use the adhesive in a range of 40 parts by weight per 100 parts by weight of the pressure-sensitive adhesive.

When the amount of surfactant used exceeds 40 parts by weight, it is not preferable because the cohesive force of the solvent-free pressure-sensitive adhesive decreases.

On the other hand, the lower limit of the amount of surfactant (5) to be used is determined for the purpose of safely controlling the polymerization heat of the polymerizable α,β-unsaturated compound (Q) and for its superiority as a solvent-free pressure-sensitive adhesive. In order to achieve both the objective of exhibiting the desired characteristics, the amount should be 0.1 part by weight or more as mentioned above.For example, when using a higher alcohol ethylene oxide adduct, which is a nonionic surfactant, The effect of improving the melt coating suitability of the product can be seen when the amount of surfactant (5) used is 3 to 5 parts by weight.In this way, when the amount of surfactant (5) used is relatively small, polymerization The object of the present invention can be achieved by sequentially adding the polymerizable α,β-unsaturated compound (Q) into the surfactant (5) as a medium without charging the entire amount at once and polymerizing the compound.

As mentioned above, an object of the present invention is to provide an industrially useful solvent-free pressure-sensitive adhesive.

The present inventors have discovered that the surfactant (5) that is ultimately contained in the product acts to improve the melt coating suitability as in the above example, or in some cases acts as a tackifier. It has been shown to have the effect of improving adhesive properties by acting on
They found that it has the effect of positively adding an effective effect to various properties as a solvent-free pressure-sensitive adhesive, but within the above range, the use of a surfactant is The amount can be changed freely.

In the present invention, by using the surfactant and the resin (B) in combination, the effect of the surfactant (5) can be further reinforced, making it possible to more safely control the polymerization heat. It also becomes possible to easily adjust the molecular weight and molecular weight distribution. Therefore, the resin (B) can be used without any restriction as long as it is a polymerizable α,β-unsaturated compound (Q) that can be converted into a liquid state in the polymerization temperature range.

Furthermore, as an example of an actual manufacturing procedure, polymerizability α.

β-unsaturated compound (if Q is liquid at room temperature or under Fi, M combination conditions, the α, β-unsaturated compound (resin [F] in all or part of Q) is dissolved in advance. It is also possible to carry out the polymerization reaction after the polymerization reaction is carried out. By using the resin (b) in this way, it is possible to safely control the heat generation during polymerization, which is one of the objectives of the present invention. For example, even a thermosetting resin such as a phenolic resin can be used as the resin (B) by selecting the polymerization temperature.

Another effect of the resin (B) is that among solvent-free pressure-sensitive adhesives, it is preferable to use a resin that can add a positive effect to adhesive properties. It has been recognized that such resin (B) can exhibit the effect as a tackifier, which is known in, for example, rubber-based adhesives, in the case of the solvent-free pressure-sensitive adhesive of the present invention.

Therefore, here, the resin (
B) includes, for example, rosin and/or its derivatives;
Terpene-based and/or terpene-phenolic resins, coumaron resins and/or coumaron-indene resins, aliphatic and/or aromatic petroleum resins, phenolic resins and/or xylene resins, ethylene-vinyl acetate, styrene-maleic [t= Mention may be made of various natural and synthetic resins such as polymers. These can be used alone or in a mixture. When surfactant (4) and resin (b) are used together, the total amount of both is usually 0.1 to 60 parts by weight based on 100 parts by weight of the resulting solvent-free pressure-sensitive adhesive.
Preferably, parts by weight are used.

Next, the polymerizable α,β-unsaturated compound (C
IK includes monomers that can be polymerized to produce pressure-sensitive adhesive properties. For example, acrylic monomers generally include ethyl acrylate,
Acrylic esters such as butyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate, or methacrylic esters such as ethyl methacrylate and butyl methacrylate are used. A functional monomer and a modifying monomer that can be copolymerized with this are usually used together as a copolymerizable monomer. Examples of functional monomers include acrylic acid, methacrylic acid, maleic anhydride, maleic acid monoester, itaconic acid, 2-hydroxyethyl acrylate, dimethylaminoethyl acrylate, N-methylolacrylamide, acrylamide, ( Examples include glycidyl meth)acrylate. Vinyl ethers, vinyl esters, butylene, acrylonitrile, etc. can be used as the modifying monomer. Further, in the present invention, compounds having two or more α,β-unsaturated bonds in one molecule can also be used for the purpose of increasing the cohesive force of the polymer.

The procedure for producing the solvent-free pressure-sensitive adhesive of the present invention is as follows:
As already explained, in the presence of a predetermined amount of surfactant (4),
Alternatively, it consists of polymerizing a monopolymerizable α,β-unsaturated compound 0 in the coexistence of a surfactant and a resin (B), and various radical polymerization methods such as a radical polymerization initiator, light or radiation are used during the polymerization. This can be done by any method using, etc.

In this case, a method using a radical polymerization initiator is preferred. As the radical polymerization initiator, a commonly known initiator such as a peroxide initiator such as benzoyl peroxide or lauroyl peroxide, or an azo initiator such as azobisinbutyronitrile or azobismethylvaleronitrile is used. It will be done.

The amount of the polymerization initiator used is usually 0.01 to 5 weight percent based on the total amount of the polymerizable α,β-unsaturated compound.

The polymerization temperature must be selected depending on the decomposition temperature of the polymerization initiator, but it can usually be selected within the range of 0 to 200°C. Polymerization time is usually 1 to 24 hours.

In order to adjust the melt viscosity of the copolymer, a known chain transfer agent may be used if necessary. Examples of chain transfer agents include mercaptans and halides.

The polymerization method and operation procedure can be freely selected depending on the polymerization apparatus, type, operation efficiency, etc. Further, during this polymerization process, necessary additives may be added depending on the purpose, such as using wax as an adhesion modifier at the same time.

The solvent-free pressure-sensitive adhesive obtained in the above manner can be applied directly to so-called adhesive processed products such as adhesive tapes and labels using a hot melt coating machine, and can be used as a laminating or bonding agent. However, if necessary, other components such as epoxy resins, isocyanates, melamine resins, urea resins, polyvalent metal salts, etc. may be added as crosslinking agents to the extent that melt coating is possible.・Additives such as general tackifiers, plasticizers, preservatives, flow control agents, etc. can also be mixed and used. Further, coloring agents such as pigments and dyes, or drugs having medical effects may be added as appropriate depending on the use and purpose. Furthermore, irradiation with active energy rays such as electron beams and ultraviolet rays after melt coating is effective in improving the cohesive force of the solvent-free adhesive obtained by the present invention.

EXAMPLES The present invention will be described below in more detail by describing examples, but the present invention is of course not limited to these examples. In the examples, "parts Jij: r parts by weight" are indicated.

Example 1 A five-loaf flask used for ordinary solution polymerization with a capacity of 500 cc equipped with a dropping funnel, a reflux condenser, a stirrer, a thermometer, and a nitrogen gas inlet tube was equipped with a nonionic surfactant, Softanol 30 (Nippon Shokubai Chemical Co., Ltd.). (manufactured by Kogyo Co., Ltd.) 100
200 parts of butyl acrylate, 50 parts of vinyl acetate, 5 parts of acrylic acid and 0.5 part of benzoyl peroxide were added thereto and heated to 80°C. followed by 80
After continuing the polymerization at 120°C for 3 hours, the polymerization temperature was raised to 120°C. Additionally, 100 parts of butyl acrylate, 2 parts of vinyl acetate
5 parts of 2-hydroxyethyl acrylate and 0.2 parts of Barhexa 3M (manufactured by NOF Corporation).
It was added in 0 minutes, and the polymerization was continued at 120° C. for 6 hours to complete the polymerization.

Polymerization could be carried out safely without any rapid generation of heat observed throughout the entire polymerization process, and an almost colorless and transparent solvent-free pressure-sensitive adhesive was obtained. When this was applied onto a polyester film at 140°C, an extremely smooth adhesive layer could be obtained.

Example 2 Using the same equipment as in Example 1, Softanol 3
50 parts of Softanol 300 (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.), a nonionic surfactant, and resin CB instead of 0.
) as Super Ester A-100 (Arayo Chemical Industry Co., Ltd.
Polymerization was carried out in the same manner as in Example 1 except that 50 parts of rosin ester resin (softening point: 100° C.) manufactured by Co., Ltd.) was charged into a flask.

No sudden heat generation was observed during the entire polymerization process.
Polymerization could be carried out safely, and in this case a pale yellow solvent-free pressure sensitive adhesive was obtained. When this was coated on a polyester film at 140°C, an extremely smooth adhesive layer could be obtained, and an adhesive film with better tackiness than Example 1 was obtained.

Claims (1)

[Claims] 1. A resin that is solid at room temperature and can be liquefied in the presence of surfactant (5) or by heating and melting with surfactant (4).
A solvent-free pressure-sensitive adhesive composition obtained by polymerizing a polymerizable α,β-unsaturated compound (Q) in the coexistence with B).