JPH0198676A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide a pressure-sensitive adhesive compsn. improved in adhesion perticularly at low temps., by incorporating a specific rosin sorbitan ester as a tackifier into an elastomer and a plasticizer as the main components to the compsn. CONSTITUTION:In a pressure-sensitive adhesive compsn. comprising an elastomer, a tackifier and a plasticizer as the main components, the tackifier used is a compd. prepd. by condensing rosin with sorbitol or sorbitan at a molar ratio of 1:1-3:1 in a solvent or without any solvent in the presence or absence of a catalyst in an inert gas atmosphere. This compsn. does not undergo crystallization, and has a good adhesion, a good tack particularly at low temps. and an excellent stability at low temps., as compared with conventional adhesive compsns. comprising a rosin ester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to pressure sensitive adhesive compositions such as pressure sensitive adhesives, hot melt adhesives, and laminating agents. More specifically, the present invention relates to a pressure-sensitive adhesive composition containing a rosin-based tackifying resin and having improved tackiness at low temperatures.

[Prior art]

Adhesives are required to have three major properties: adhesive strength, adhesion strength, and cohesive strength, and usually consist of an elastic body that provides cohesive strength, a tackifier that provides adhesive strength, and a plasticizer, and if necessary, It is manufactured by appropriately adding and blending antioxidants, fillers, colorants, extenders, etc. Natural rubber and various synthetic polymers are used as elastic bodies that provide cohesive force, and 1 is used as a tackifier.
Petroleum resins, rosin derivatives, and terpene resins are mainly used. Among these, rosin derivatives generally have excellent solubility in a wide range of solvents, compatibility with various elastic bodies, adhesive properties, and adhesive strength compared to other tackifiers.
Widely used. The main components thereof are rosin, polymerized rosin, and their hydrogenated products, such as glycerin and pentaerythritol esters (hereinafter referred to as rosin esters).

[Problem that the invention seeks to solve]

Rosin esters have features as tackifiers, but on the other hand, it has been pointed out that their drawback is that they tend to cause a decrease in adhesive properties at low temperatures due to the aggregation phenomenon unique to rosin esters. In particular, there is a remarkable tendency for adhesive strength (hereinafter referred to as tack) to decrease over a long period of time, such as 3 or 6 months at a low temperature such as 0°C.

This is true for both solvent and emulsion types. Improving low-temperature tack can usually be solved by increasing the amount of process oil and softeners such as plasticizers, but on the other hand, the cohesive force decreases and the plasticizer migrates, which tends to cause problems such as stains. The reality is that there is a need for a tackifier that takes advantage of the characteristics of tackifiers and has excellent adhesion even at low temperatures.

[Object of the present invention] Book 5I! An object of the present invention is to provide a pressure-sensitive adhesive composition that has particularly excellent low-temperature adhesive properties.

[Means for solving problems]

From these viewpoints, the present inventors have made extensive studies to obtain a new adhesive, and have found that a composition containing a rosin sorbitan ester (hereinafter referred to as the compound of the present invention) obtained by the method of the present invention meets these objectives. This discovery led to the present invention.

The pressure-sensitive adhesive composition obtained using the compound of the present invention has the following features compared to adhesive compositions obtained from conventional rosin esters.

(1) The tackifier does not crystallize, and the composition blended with the elastic body also does not crystallize and exhibits good adhesive strength, especially low-temperature tack.

(2) Since it has a rosin-based lipophilic group and a cyclic polar group (OH group, ester group, ether group) in the molecule, it has a wide range of solubility and compatibility with solvents and elastic bodies.

(3) Particularly good compatibility with acrylic base polymers.

[Structure of the invention]

Rosin in the present invention includes abietic acid, parastric acid, neoabietic acid, bimaric acid, isobimaric acid,
Tall oil is a general term that includes cyclocyclic carboxylic acids such as dehydroabietic acid and sandaracopimaric acid, their unsaponifiables, small amounts of fatty acids, oils, and their disproportionated and hydrogenated products. rosin, wood rosin,
Gum mouth.

It usually contains all the resin acids called gin, etc.

It is obtained as a mixture of the various carboxylic acids mentioned above, mainly consisting of dehydroabietic acid and abietic acid.

The compound of the present invention can be prepared by combining rosin and sorbitol or sorbitan in a mol range of 1:1 to 3:1 in the presence of an acid or alkali catalyst, or in a solvent without a catalyst, or in the presence of an inert gas without a solvent. It is obtained by dehydration condensation. Its composition mainly includes sorbitan or sorbite ester, some rosin, and oil decarboxylated in the reaction, but it is usually obtained as a mixture of these. For the purposes of the present invention, the molar ratio of rosin is preferably 1.5 to 2.5 mol to 1 mol of sorbitol or sorbitan, with an acid value of 20 or less and a softening point of 70 to 130.
A compound of the invention is obtained at .

When a disproportionated rosin is used, a compound of the present invention having good weather resistance can be obtained.

The reason why the adhesive composition containing the compound of the present invention does not cause a decrease in adhesive strength especially at low temperatures is that the compound of the present invention -
It is obtained by reaction with a polyfunctional alcohol having 4 to 6 OH groups, and is mainly composed of monoester, diester, or triester of sorbitan, monoester or diester of sorbite, and is an etheric cyclic ester containing oxygen. This is presumed to be due to the fact that it is a mixture of similar and various types of esters, and although each individual ester itself has its own softening point, as a mixture they are intricately intertwined and prevent crystallization at low temperatures. It is believed that a good adhesive composition can be obtained.

For example, in systems containing glycerin triester of rosin, diester of ethylene glycol of rosin, etc., it is difficult to prevent crystallization at low temperatures, and it is difficult to prevent a decrease in adhesive strength.

The compound of the present invention is used as a tackifier together with an elastomer that provides cohesive force and a plasticizer, and these elastomers include elastomeric polymers conventionally used in pressure-sensitive adhesives, such as natural Rubber, polyisoprene, polybutadiene, styrene-butadiene copolymer, polychloroprene, etc. can be used, and in any case, a composition with extremely good compatibility can be obtained. The compound of the present invention and the elastic body can be used. There is no particular restriction on the blending ratio with the plasticizer, but for example, in the case of a pressure-sensitive adhesive, the compound of the present invention may be added in an amount of 30 to 15 parts by weight per 100 parts by weight of one elastic body.
0 parts by weight, preferably 65 to 150 parts by weight, more preferably 70 to 100 parts by weight. As a plasticizer, one or two types such as high boiling point solvent, mineral oil, process oil, ordinary adipic acid type, or phthalate type are used.
More than one species is used.

Moreover, the plasticizer is 40 to 15 parts by weight per 100 parts by weight of the elastic body.
0 parts by weight is preferred. This pressure-sensitive adhesive can be applied to various adhesive tapes including transparent tape, labels, name plates, road signs, albums, wallpaper, and laminates such as bonding plastics together or metal and plastic. Furthermore, when the compound of the present invention is blended with a thermoplastic resin and/or wax, it can be used as a hot melt adhesive composition. It can also be used by mixing it with ordinary rosins, petroleum resins, terpene resins, etc. in appropriate proportions and blending it with thermoplastic resins and/or waxes.

Thermoplastic resins that can be used for this purpose include:
Examples include ethylene-vinyl acetate copolymer, polystyrene, polypropylene, polyamide, polyester, styrene-butadiene/block copolymer, polyvinyl acetate, polyvinyl ether, polyurethane, polyacetal, butyl rubber, and the like.

Further, examples of the wax neck include paraffin wax, microcrystalline wax, low molecular weight polyethylene wax, Fischer-Tropsch wax, and carnauba wax. There is no particular restriction on the mixing ratio of these, but a preferred mixing ratio for a hot melt adhesive composition is 40 to 80 parts by weight of the compound of the present invention, 4 parts by weight of the thermoplastic resin.
0 to 80 parts by weight and 0 to 40 parts by weight of waxes. It is also possible to obtain a composition with excellent adhesive properties by emulsifying the compound of the present invention using a solvent, oil, plasticizer, etc. and then adding it to a polymer emulsion.

Polymer emulsions include vinyl acetate, ethylene-
Vinyl acetate, vinyl acetate-acrylic.

Examples of emulsifiers for emulsifying the compounds of the present invention include acrylic, acrylic-styrene, and styrene-butadiene bases, as well as nonionic surfactants having polyoxyethylene chains, and their sulfuric esters, phosphoric esters,
Various anionic activators such as sulfonates and carboxylates, combinations of anionic activators and nonionic activators, etc. can be mentioned.

〔Example〕

Examples of the present invention are shown below. However, the present invention is not limited to the following examples. In the examples, all parts indicate parts by weight.

(Synthesis example 1) I equipped with a thermometer, nitrogen inlet tube, condenser, and stirrer
In a Q-four flask, 340 parts of rosin (2°0 mol),
The compound of the present invention (compound A ) was obtained.

(Synthesis Example 2) Using the same method as in Synthesis Example 1, using modified rosin (3.0 mol) and sorbitol powder (1.0 mol), a resin with a softening point of 105°C to 110°C, an acid value of 30, and transparent at room temperature was prepared. A solid compound of the present invention (referred to as compound B) was obtained.

Example 1 (pressure-sensitive adhesive composition) and Comparative Example 1 Compounds A and B, styrene-butadiene synthetic rubber (SBR
) were dissolved in toluene to obtain the solid content of compounds A and B:
SBR Nidioctyl phthalate (D0P) = l 00
: 100 : 20 parts of l were blended to prepare a pressure sensitive adhesive.

Polyester film (Toshi Lumira-25, thickness 25μ
) with an applicator (film thickness 25μ)
) and dried in a hot air dryer (100°C) for an hour, and then left to stand in a constant temperature room for 24 hours to prepare an adhesive tape for testing. Using this tape, the adhesive force, adhesive force, and cohesive force of this pressure-sensitive adhesive were measured by the following methods. The results are shown in Table 1.

For comparison, hydrogenated rosin glycerin ester (
The softening point was 68° C. and pickling in vinegar 8) was also carried out at the same time.

Adhesive strength: Judged by finger touch.

(Good ○ → Δ → × Bad) Adhesive crab JIS Z-1528 Cohesive force: The created adhesive tape was crimped (300 mm/ n+in
3 round trips). Lower a 500g weight onto the edge of the tape and
The sample was placed in a constant temperature bath at 0° C. and the time (IIlin) until the tape was peeled off and the weight fell was measured.

Table 1 The results of Example 1 show that the composition of the present invention is a good pressure-sensitive adhesive.

Example 2 (compatibility with resin) Synthesis example 1. A solution containing Compound A and base resin in a ratio of 50:50 was applied to a glass plate, and the transparency of the dried coating film after the solvent was removed was examined to determine compatibility. (○: compatible, ∆ partially compatible, ×: incompatible) The results are shown in Table-2.

It can be seen that the compounds of the present invention have good compatibility with most base resins.

Examples 3-4 (Comparative Example 2) (Low temperature tack) Synthesis example 1. Compound A of Synthesis Example 2 and Compound B of Synthesis Example 2 were blended in a ratio of compound of the present invention/natural rubber/dioctyl phthalate (DOP)=100:80:100 to prepare a pressure-sensitive adhesive. As a comparative example, a pressure-sensitive adhesive was prepared in the same manner using rosin glycerin ester (softening point: 85°C, ugly value: 6). This was diluted with a toluene solution, applied onto a polyester film, and dried to produce a pressure-sensitive adhesive tape.

Korogaritakku (*) was measured at temperatures of 25°C, 10°C, and 0°C. Comparison amounts were also made in the same manner. The results are shown in Table-3.

*Korogari tuck: Dow style, the number is the ball number.

Table 3 Examples 5 to 6 (Comparative Example 3): Low-temperature stability of adhesive strength Compounds A and B of Synthesis Examples 1 and 2 were used to create an emulsion according to the following formulation.

Compound of the present invention 50.0 parts Dioctyl phthalate 15.0 Toluene
7.0 surfactant 1.2 go
Total 100.0 100 parts of this emulsion, SBR latex (solid content 40%)
) was added to make it uniform and an emulsion type adhesive was prepared.As a comparative example, rosin glycerin ester (softening point 85
℃ and an acid value of 6). This pressure-sensitive adhesive was stored at 5° C. for 3 months, then applied onto a polyester film and air-dried to produce a pressure-sensitive adhesive tape. Adhesive force and cohesive force were measured in the same manner as in Example 1. As for the adhesive strength, the Dow formula was used as in Examples 3 and 4. The results are shown in Table 4.

〔Effect of the invention〕

From the examples, it is clear that the adhesive composition of the present Fukomei has low temperature tack,
It is clear that the adhesive composition has excellent adhesive strength and stability at low temperatures.

Claims (4)

[Claims] (1) A pressure-sensitive adhesive containing an elastic body, a tackifier, and a plasticizer as main components, which contains one or more compounds obtained by dehydration condensation of rosin and sorbitol or sorbitan as the tackifier. A pressure-sensitive adhesive composition characterized by: (2) Softening point 70-1 obtained by reacting 1-3 moles of rosin with 1 mole of sorbitol or sorbitan
The composition according to claim 1, which exhibits a temperature of 30°C. (3) The ratio of elastic body/tackifier/plasticizer is 1
00 parts, 30 to 150 parts of tackifier, 30 parts of plasticizer
150 parts of the composition of claim 1. (4) The composition according to claim 1, wherein the pressure-sensitive adhesive is a solvent-free type, a solvent diluted type, or an aqueous emulsion type.