JPS60226579A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide the titled composition of such a degree of adhesive force as to be preventive from damaging adherend surface, giving good adhesive characteristic even for coarse surface such as of corrugated board, comprising two sorts of specific styrene-isopropylene block copolymers and adhesivity-affording resin in specified proportions. CONSTITUTION:The objective composition comprising (A) 100pts.wt. of a block copolymer of formula S1-I1 type [S1 is styrene (analogue)-derived block polymer, the S1 content in said copolymer <=15wt%; I1 is isoprene (analogue)-derived block polymer], (B) 1-50pts.wt. of a second block copolymer of formula (S2-I2n-S3 type [S2 and S3 are each styrene (analogue)-derived block polymer, the styrene content in said copolymer <=10wt%; I2 is isoprene (analogue)-derived block polymer, the number-average molecular weight >=150,000; n is 1-5] and (C) 50-300pts.wt. of an adhesivity-affording resin.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a pressure-sensitive adhesive composition, a method for producing the composition, and a single-sided or double-sided pressure-sensitive adhesive tape/sheet or similar products using the composition. It relates to an adhesive article consisting of an article, and more specifically, it is mainly composed of a block copolymer consisting of styrene and isoprene, and can be peeled off without damaging a surface having relatively weak interlaminar strength, such as a paper material. A pressure-sensitive adhesive composition that exhibits a certain level of adhesion strength and good retention performance due to minute cohesive failures at the adhesive interface of the adhesive layer even on a surface to which it is applied having a rough surface such as paper material; The present invention provides adhesive articles such as tapes, sheets, or labels using the composition.

<Prior art and its problems> Pressure-sensitive adhesive compositions used for adhesive tapes for packaging, adhesive tapes for paint masking, and adhesive labels that adhere to the surface of an adherend by applying light pressure to the surface of the adherend include natural adhesives. There are known rubber-based types that have a rubber component as a main component, such as rubber, and resin-based types that have a resin component as a main component, such as an acrylic resin.

These rubber- or resin-based pressure-sensitive adhesive compositions generally have a polymer constituting the main component dispersed in water or dissolved in an organic solvent. Due to the surfactant added during the production of the composition, there is a problem that the water resistance of the resulting adhesive product is poor, and in the case of solvent-based products, it is necessary to volatilize the solvent during the production of the adhesive product. However, there is a problem in that it may impair the health of workers or pose a risk of fire, and therefore requires a large solvent recovery device.

Recently, hot-melt or high-concentration pressure-sensitive adhesive compositions that use no or almost no surfactants or organic solvents have been developed as pressure-sensitive adhesive compositions that solve the problems of water-dispersed or solvent-based adhesives. Compositions are being developed and used.

A typical one of these adhesive compositions, which has a styrene-isoprene-styrene block copolymer as its main component, is excellent in coating work during hot-melt coating, and is suitable for use in solvent-based adhesive compositions, for example. Coating can be done several times faster than conventional products, so
It has great advantages in terms of economy and non-pollution.

However, pressure-sensitive adhesive compositions containing a styrene-isoprene-styrene block copolymer as a main component are less practical in practical use than, for example, natural rubber-based adhesive compositions, which are the mainstream of rubber-based pressure-sensitive adhesive compositions. It has the following drawbacks in adhesive performance.

(b) Adhesive properties are insufficient for adherends with rough surfaces such as corrugated paper or plywood, and if adhesives are pasted on these adherends and left for a long period of time, the adhesive may deteriorate. The article gradually peels off from the adherend surface due to shrinkage of the article itself, external force applied to the article, and the like.

(b) If an external impact is applied to the attached adhesive article, it will easily peel off because it lacks the ability to absorb and alleviate the impact.

(c) If the surface of the object to be adhered is smooth or the interlayer strength of the surface layer is weak, peeling off the adhesive article once applied for the purpose of adjusting the position will damage the surface of the object.

(b) When cutting adhesive articles using a cutting tool such as a tape cutter or scissor, glue adheres to the edge of the blade, making it difficult to cut or cutting diagonally.

In practice, these drawbacks, for example, in case (a), significantly reduce reliability in the quality of adhesive products, and in case (b), one of the typical uses of adhesive products such as adhesive tapes. If used to seal a cardboard box, it will be opened unexpectedly during transportation. In the case of (c), if you use an adhesive product such as adhesive tape to fix the masking film when wrapping the surface-painted furniture or painting the wall surface, it is recommended that the masking film be fixed when peeled off after use or when the masking film is applied. When correcting incorrect pasting during work, the adherend may be damaged, and in the case of (2), sealing work on cardboard boxes, etc. must be stopped only while the glue on the cutting edge is removed and cleaned. It is.

Various efforts have been made to solve these drawbacks (a) to (a). For example, as a solution to (a), Japanese Patent Application Laid-open No. 146537/1983 discloses a structure of a styrene-inprene-styrene block copolymer. It is recommended to use a specific styrene material in JP-A-49-53633, JP-A-53-72047, JP-A-56-50978, and JP-A-58-89672. Combining an isoprene-styrene block copolymer with a specific adhesion-imparting resin has also been proposed in JP-A-55
JP-A-149360 and JP-A-56-50980 each propose the use of a modified structure of the adhesion-imparting resin added to the block copolymer.

However, what these proposals have in common is that they have superior adhesion and cylindrical holding power to objects with smooth surfaces such as stainless steel plates, and in this respect conventional rubber Although it exhibits superior properties compared to other pressure-sensitive adhesive compositions, the drawbacks (b) to (d) above are exacerbated.Moreover, the adhesive tape obtained by the above proposal Adhesive articles are generally considered to have high cohesive properties, so if they are pasted on the surface of an adherend with strong pressure, the desired adhesive properties can be obtained, but the contents may be soft or easily damaged by pressure. In the case of sealing cardboard boxes, where it is difficult to apply strong pressure due to the roughness of the adhesive, it is difficult to obtain the desired adhesive properties. The shortcomings are reinforced.

In view of the state of the prior art, the present inventors conducted various experiments using a conventional nostyrene-isoprene-styrene block copolymer. As a result, many of the above-mentioned drawbacks are due to the unique physical properties of the copolymer, and are caused by the adhesion-imparting resin, low softening point adhesion-imparting resin, oil, etc. added to the copolymer. Even if the structure, type, and blending amount of the softening component etc. are changed, it will not provide an essential solution.On the contrary, if the adhesive properties are improved by these additives, the above-mentioned (a), (b) and Therefore, the object of the present invention is to provide a pressure-sensitive adhesive composition that solves all the drawbacks of (a) to (a) above, and to provide a pressure-sensitive adhesive composition that solves all of the drawbacks of (b) to (b) above. An object of the present invention is to provide an adhesive article such as an adhesive tape made of the present invention.

Other objects of the invention will be understood from the following description.

<Structure of the Invention> The object of the present invention is to obtain a block copolymer of the general formula S, -I (in the formula, S is d from styrene or a styrene homolog).
S for the block polymer derived and for the copolymer
, the content is 15 or less times, and II is a block polymer derived from imprene or an isoprene analogue. ) per 100 parts by weight, the general formula (S, -I,
) n-Sll type block copolymer (82 and S8 in the formula
is a block polymer derived from styrene or a styrene homolog, and the styrene content of the copolymer is 1
0 weight or less, is a block polymer derived from I21d isoprene or an isoprene analog, and has a number average molecular weight of 150,000 or more (on is an integer from 1 to 5)
This is achieved by blending the adhesive composition so as to contain 1 to 50 parts by weight and 50 to 300 parts by weight of the adhesion-imparting resin.

According to the pressure-sensitive adhesive composition of the present invention and an adhesive article such as an adhesive deso made using the composition, it is possible to peel off surfaces such as paper materials and plywood with relatively weak surface interlayer strength without damaging them. It has the characteristics of exhibiting a certain degree of adhesive strength and good retention performance against fine cohesive failure at the bonding interface of the adhesive layer even when the surface of the adherend is rough.

By the way, prior to the present invention, the present inventors had developed a pressure-sensitive adhesive composition in which the number average molecular weight of the styrene block polymer per block was 1oooo or less as a pressure-sensitive adhesive composition that exhibited good retention performance due to the above-mentioned fine cohesive failure. Some products have a styrene-isoprene-styrene block copolymer as the main component, and some have a styrene-inprene block copolymer as the main component, and the tensile strength of regular products is 10 ha.
We have found that a material with a value of /lx□ or less and a breaking elongation of 500% or more is good and has filed an application. Although such a composition solves most of the above-mentioned drawbacks (a) to (a), it is difficult to use adhesive products such as adhesive tapes stored at high temperatures, especially at 40°C or higher (for example, in summer). The adhesion properties under high humidity, such as the adhesive strength when pasted on the surface of the adherend, and the holding power when the adhesive article is pasted on the surface of the adherend and stored at 40°C or higher, are insufficient. It was sufficient.

The adhesive composition of the present invention solves the above-mentioned drawbacks (a) to (a) and also satisfies the adhesive properties at high temperatures described above. The block copolymer (5) represented by the formula SI I2 is a styrenic block polymer in which S St is derived from styrene or a styrene analog, and the SI content with respect to the copolymer is 15% by weight or less, and 11 is It is an imprene block polymer derived from isoprene or isoprene analogs.

The number average molecular weight of the copolymer (3) is 100,000 to 10
00000 is preferably used.

As the styrenic block polymer, in addition to styrene, homologs to which functional groups such as methyl groups and nitrile groups are added by conventional methods can also be used, but the content is 3 to 10% by weight.
is preferable; if it exceeds 15% by weight, the rubber elasticity of the pressure-sensitive adhesive composition will be markedly reduced, and the desired adhesive properties cannot be obtained. Preferred isoprene-based block polymers include those having a number average molecular weight of about 40,000 or more and containing 85% by weight or more in the copolymer.

Furthermore, the general formula (S,
-I, )n-S, block copolymer (B)
Ha, S! and S8 is a styrenic block polymer derived from styrene or a styrene homolog, and the styrene content of the copolymer is 10% by weight or less;
is an isoprene-based block polymer derived from isoprene or isoprene analogs, and has a number average molecular weight of 11!
The styrene content is preferably 2 to 8% by weight, and if it exceeds 10% by weight, the rubber elasticity of the pressure sensitive adhesive composition decreases;
The desired adhesive properties cannot be obtained. In addition, the number average molecular weight of the isoprene block polymer is 15,000.
If it is less than 0, it is not preferable because the cohesiveness becomes too high, and 200,000 to 5oooooo is practically desirable.

The structure of the copolymer (81) may be radial (n in the general formula is 2 to 5) or linear (n = 1), but a linear structure with fewer branches is preferable. This is preferable in terms of adhesive properties.

Therefore, the blending amount of the block copolymer (Bl) is 1 to 1 to 100 parts by weight of the block copolymer (A).
It is important to keep the amount in the range of 50 parts by weight; if it is less than 1 part by weight, the adhesive properties of the pressure-sensitive adhesive composition at high temperatures will be insufficient, and if it is more than 50 parts by weight, the adhesive properties of the pressure-sensitive adhesive composition will be insufficient. This is undesirable since the hot melt viscosity or solution viscosity becomes too high and the coating workability is poor, and the practical amount is within the range of 3 to 45 parts by weight.

The block copolymer (5) and (B) are obtained by living or anionic polymerization using Fi and an alkyl lithium-based initiator.

That is, an organolithium compound such as n-butyl lithium or 5ee-butyl lithium is added to an inert solvent selected from hydrocarbons such as styrene, benzene, cyclohexane, and n-hexane, and then styrene, vinyl While sequentially adding aromatic vinyl heptamers such as toluene, vinylxylene, and α-methylstyrene, and homologous monomers such as imbutylene and methylisoprene, each block is typically heated at a temperature of 20 to 70°C. This is what you get from forming traps.

Copolymer fBl can also be obtained by coupling a copolymer with a coupling agent such as tin tetrachloride, polyepoxide, divinylbenzene, divinyltoluene.

In addition, these copolymers (5) and (BI Fi, US Pat. No. 3,787,531, US Pat. No. 3,281,383,
It can also be obtained by the method described in Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 40-24914, etc. ◎ The adhesion-imparting resin imparts appropriate adhesive strength to the pressure-sensitive adhesive composition, and For example, one or more of rosin resin, terpene resin, terpene modified resin, coumaron indene resin, petroleum resin, styrene resin, etc. can be used.

The resin contains 50 to 300 parts by weight, preferably 70 to 2 parts by weight of adhesion-imparting resin per 100 parts by weight of the copolymer.
A suitable pressure-sensitive adhesive composition can be obtained by blending within the range of 0.00 parts by weight. If the amount of the resin exceeds 50 parts by weight, the adhesive strength will be too high and the retention performance on rough surfaces will decrease, which is not preferable.

Known compounding agents such as fillers, pigments, softeners, plasticizers, and anti-aging agents can be added to the pressure-sensitive adhesive composition of the present invention. For example, rubbers such as stranded natural rubber, styrene-butadiene rubber, polyisobutylene rubber, polybutadiene rubber, butadiene-nitrile rubber, or polymers such as acrylic polymers can be mentioned. The addition of these rubbers or polymers serves to improve other desired properties of the pressure sensitive adhesive composition, such as cold resistance.
The amount of these rubbers or polymers added is determined by the amount of the copolymer (
The amount must not exceed 50 parts by weight based on 1100 parts by weight of A1, and if it exceeds 50 parts by weight, the hot melt viscosity or solution viscosity of the pressure sensitive adhesive composition will increase significantly, and the tape support film Otherwise, it is undesirable because the workability of coating onto sheet-like objects decreases.

The pressure-sensitive adhesive composition of the present invention having such a composition solves the above-mentioned drawbacks (a) to (a) and exhibits excellent adhesive properties even at high temperatures. To ensure more effective results,
The above-mentioned copolymer (4) (Bl and adhesion-imparting resin, as well as the type, combination, or blending amount of rubber or polymer and compounding agents, etc., are selected, and the tensile strength at room temperature (20°C) is 10 V or less, preferably 0. .1 to 7 VcII", and the elongation at break is 500% or more, preferably 800%.
It is desirable to design the values to be within the range of ~2500%.

When the tensile strength exceeds 10ψ', the adhesive force becomes too high and peeling occurs at the adhesive interface with the adherend, resulting in poor shear resistance against external impact and peeling due to impact. If the elongation at break is less than 500%, the adhesive force will be too low and the impact resistance and creep resistance will be poor, which is not preferable.

The pressure-sensitive adhesive composition of the present invention is usually charged into the hopper of an extruder, heated at 150 to 200°C, and heated to 1000 to 200°C.
It is melted to 4,000 pores and applied to the surface (one or both sides) of a tape support such as a plastic film or sheet, paper, woven fabric, non-woven fabric, foil, etc. to a thickness of 5 to 300 μm, and is used as an adhesive tape, etc. adhesive articles are made.

<Effects of the Invention> As described above, the pressure-sensitive adhesive composition of the present invention contains a specific styrene-inprene block copolymer, a specific styrene-isoprene-styrene block copolymer, and an adhesion-imparting resin. Since it is blended within a specific range, it has the characteristics of having a strong adhesive strength that does not damage the surface of the adherend and good adhesive properties even on rough surfaces such as corrugated paper. When the tensile strength is set to 10 walls i or less and the elongation at break is set to 500% or more, the above effects are more reliably, practically and accurately exhibited.

<Example> Examples of the present invention will be shown below, and the tensile strength and elongation at break were measured by the following method.

<Tensile strength and elongation at break> A strip-shaped sample piece (pressure-sensitive adhesive composition/piece) with a thickness of 0.2 fl and a width of 5 fins was fixed at both ends in the length direction with a chuck interval of 10 fl, and then tensile Speed 50fi/m1n (conditions 20~
The tensile strength and elongation of the sample piece at break are measured by pulling the sample piece at 25°C).

In the following examples, parts by weight are meant by parts by weight.

Example 1 Styrene monomer 259 was dissolved in cyclohexane 41 as an inert solvent, and 2 g of n-hexane solution containing 0.2 g of sec-butyl lithium was added to 60
℃ to polymerize, then add 544 g of isoprene monomer to polymerize, age for 24 hours, add phenolic antioxidant 109 and 5 cc of methyl alcohol, coagulate, and form a styrene-isoprene block. ◇This copolymer consists of a styrene block polymer having a number average molecular weight of about 1000 and a styrene block polymer having a number average molecular weight of about 2000.
The styrene content was approximately 5% by weight.

Similarly, 13 g of styrene monomer was dissolved in cyclohexane 41 as an inert solvent, and 1 g of n-hexane containing 0.19 sec-butyl lithium was added thereto.
The temperature was raised to 0°C to polymerize, and then imprene monomer was added at 74°C.
8g was added and polymerized, and 5g of phenolic antioxidant and 2.5cc of methyl alcohol were added and coagulated to form a styrene block polymer with a number average molecular weight of about 11,000 and a number average molecular weight of about 550,000 per block. A linear styrene-isoprene-styrene block copolymer (Ble) having a styrene content of about 3.5% by weight was obtained.

Next, 6 g of copolymer (Bl) was added to 100 g of the above block copolymer (A), and these were dissolved in 500 g of toluene. Furthermore, 100 g of petroleum resin was added and dissolved until the solid content concentration was approximately A high-concentration pressure-sensitive adhesive composition of 40% by weight was obtained. In order to evaluate the properties of this composition, it was coated on a silicone-treated release paper to a thickness of 100 μm after drying and dried to form a pressure-sensitive adhesive. Two sheets of the film were obtained and the tensile strength and elongation at break were measured, and values of 2 #/- and 2000 inches were obtained, respectively.

Furthermore, an adhesive tape was prepared by applying the above composition to the surface of kraft paper so that the thickness after drying was 30 μm.

The adhesive strength of this tape was measured according to JIS Z 1522 and was found to be 12009/25ff.

In addition, the holding power of this tape was measured according to JIS Z 1524 (conditions at 40°C, the adherend was cardboard paper, the pasting area was 25 m x 10 m), and the time it took for the tape to slip off the corrugated paper was approximately 30 seconds. The peeling of the tape from the corrugated paperboard was due to fine cohesive failure at the adhesive interface of the adhesive layer.

Next, the practicality of the tape was tested using the following items.

Surface destruction test: Attach tape to corrugated paper, leave it for a while, then slowly peel off the tape. 1 point if the surface of the corrugated paper is completely destroyed, 2 points if it is partially destroyed. Corrugated box sealability test: The tape was attached to the flap butt part of a JIS A-type corrugated pole box, and the tape was rated at room temperature ( 100 pieces each were stored at 20°C and 40°C for one week, and the state of sealing of the flaps was examined and found to be 100% in each case.

Cutting test: When the tape was cut using commercially available scissors, almost no adhesive was observed even after cutting the tape over 1000 times.

Example 2 A pressure-sensitive adhesive film and an adhesive tape were prepared in the same manner as in Example 1, except that the amount of block copolymer (Bl added was 159%), and their properties were evaluated. Tensile strength: 5 kg/
ax' Breaking elongation: 2100% Adhesive strength: 13009/25 order retention crab 500 (cohesive failure) Surface failure test: 3-point corrugated pole box sealability test: 1 each at room temperature and 40'C
j100-A cutting test: 1000 times or more Example 3 In Example 1, Mooney viscosity MIJ1+4 (
100°C) 20 parts by weight of 45 strand natural rubber and 30 parts by weight of vaseline were added and uniformly dissolved.
Japanese paper impregnated with YD pack sizing agent (basis weight 289
/n/) so that the thickness after drying was 25 μm to obtain an adhesive tape for masking having a width of 18 fl.

After the tape was applied to furniture whose surface had been painted, it could be removed smoothly without damaging the surface of the furniture.

The adhesive force of this tape is approximately 280 g/25 tm, and the holding force (conditions at 40°C, stainless steel plate, area 18 x 25 M, load 500 f) is approximately 1
It was 8 minutes.

Comparative Example Between the block copolymers of Example 1 and (instead of 810, 1
Using a styrene-isoprene-styrene block copolymer consisting of a styrene block polymer (styrene content of about 14% by weight) with a number average molecular weight of about 1iooo per block and an imprene block polymer with a number average molecular weight of about 140,000, A pressure-sensitive adhesive film and an adhesive tape were prepared in the same manner as in Example 1, and their properties were evaluated as follows.

Tensile strength: 27 kfam rich elongation at break: 1600% Adhesive crab 23009/Kora 8 Holding crab 1000 or more Surface breakage test: 1 point Corrugated box sealability test: 30% at room temperature, 15% at 40°C (each This was peeling at the adhesive interface between the corrugated paper and the adhesive layer of the tape.) Cutting test = 300 times Patent applicant Sanbe Hijikata, representative of Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] 1) A block copolymer of the general formula S + It type (wherein 81 is a block polymer derived from styrene or a styrene analog, and the S1 content with respect to the copolymer is 15% by weight or less) % I+ is a block polymer derived from isoprene or isoprene homologs O) 10
0 parts by weight, a block copolymer of general formula (Sg-Is) H8i type (wherein 82 and Sll are block polymers derived from styrene or styrene analogues, and the styrene content of the copolymer is 10% by weight or less, and is a block polymer derived from isoprene or isoprene analogs and has a number average molecular weight of 150,000.
That's all. n is an integer of 1 to 5); and 50 to 300 parts by weight of an adhesion-imparting resin. 2) General formula 51-1. Claim 1: A rubber or polymer other than the Ss type block copolymer of the general formula (Sg-1x) is blended in an amount not exceeding 50 parts by weight with respect to 100 parts by weight of the type block copolymer. The pressure sensitive adhesive composition described. 3) Claims 1 to 2 whose tensile strength at room temperature is 10 #/ff” or less and whose elongation at break is 500% or more.
The pressure-sensitive adhesive composition according to any one of the following items.