JPH0211633B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hot-melt adhesive, which uses a modified product in which an unsaturated carboxylic acid or a derivative thereof is grafted onto a block copolymer consisting of a polybutadiene or polyisoprene block and a polystyrene block. The present invention provides a hot-melt adhesive composition with an excellent balance between tackiness and holding power. Conventionally, adhesives have been used for various purposes such as adhesive tapes and labels. Adhesives are applied to tapes by applying an adhesive solution prepared by dissolving the adhesive in a solvent onto a base material by means of a roll, spray, or the like. However, the use of such solvents is a problem in the production of pressure-sensitive products such as adhesive tapes in terms of pollution, fire, occupational health, etc., and has become increasingly regarded as a social problem in recent years. Therefore, as a means to solve this problem, non-solvent hot melt adhesives have recently been attracting attention, and as hot melt adhesives, block copolymers consisting of polybutadiene or polyisoprene blocks and polystyrene blocks are used. It is well known that adhesive compositions based on polymers are most suitable. however,
When these are used as adhesive tapes, the balance of characteristics of the adhesive tapes is still insufficient, and the current situation is that they cannot be put to practical use. For example, the
No. 17037 discloses a composition comprising a block copolymer consisting of a polybutadiene or polyisoprene block and a polystyrene block, an adhesive resin, and a rubber spreading oil. Also, Tokko Akira
No. 47-21720 discloses a composition comprising polyptadine or a block copolymer of a polyisoprene block and a polystyrene block, an adhesive resin, a rubber spreading oil, and an atactic polypropylene. However, among the compositions obtained from these patents, pressure-sensitive adhesive compositions using a block copolymer consisting of polybutadiene block and polystyrene block as a base polymer have excellent holding power but poor initial tackiness. Adhesive tape characteristics are unbalanced.
In addition, pressure-sensitive adhesive compositions using a block copolymer consisting of polyisoprene blocks and polystyrene blocks as a base polymer have excellent initial tackiness but poor holding power, resulting in poor balance in pressure-sensitive adhesive tape properties. Furthermore, in JP-A No. 50-56427, a polybutadiene or block copolymer consisting of a polyisoprene block and a polystyrene block modified with maleic acid, a metal oxide, a rubber developing oil, an adhesive resin, and a reinforcing resin are disclosed. Compositions are disclosed. However, these pressure-sensitive adhesive compositions have a significantly lower holding power at high temperatures because the maleic anhydride-modified block copolymer, which is the base polymer, forms ionic cross-bonds with metal oxides. Although excellent,
Initial adhesion is extremely poor, resulting in extremely unbalanced adhesive tape properties. An object of the present invention is to provide a hot-melt adhesive composition that is most suitable for producing adhesive tapes and other pressure-sensitive products using a hot-melt method that has an extremely good balance between initial tackiness and holding power. Under such circumstances, the inventors,
As a result of extensive research into hot-melt adhesives, we surprisingly discovered that an adhesive composition that uses a specific polymer and a specific adhesive resin can provide an excellent balance between initial tack and holding power. This heading led to the present invention. That is, the present invention is based on the general formula AB-
A, (A-B) _o , B(-A-B) _o , (A-B)-nA,
(AB)mX [Here, B is substantially a polybutadiene or polyisoprene block, A is substantially a polystyrene block, and n represents an integer from 2 to 10. X is a polyfunctional compound to which m polymer chains are bonded, and m represents an integer of 3 to 7. ] Flow rate (ASTM-
D1238, G conditions) is in the range of 0.1 to 40 g/10 min, and the styrene content is in the range of 5 to 50 wt%. 0.01〜
Modified products grafted in a range of 30% and the modified products
Polyterpene adhesive resin per 100 parts by weight
This hot-melt pressure-sensitive adhesive composition is characterized by comprising 20 to 200 parts by weight of a softener and 5 to 200 parts by weight of a softener, and has an excellent balance between initial tackiness and holding power, and is fully suitable for practical use. The present invention will be explained in detail below. The block copolymer used in the present invention has the general formula A-B-A, (A-B) _o , B(-A-B) _o , (A-
B)-nA, (A-B)mX [A, B, X, n in the formula
and m have the same meanings as above], and can be obtained by a living anionic polymerization method using an alkali metal as a base material and an initiator. Such block copolymers can be produced by sequentially polymerizing monomers block by block in the presence of the initiator, or by simultaneously charging two types of monomers with different copolymerization reactivity ratios. It can be obtained by a method of obtaining a living block copolymer or a method of coupling a living block copolymer using the above-mentioned initiator. The block copolymer represented by (AB)mX can be obtained by coupling the living block copolymer represented by AB with a polyfunctional coupling agent. For example, the flow rate of block copolymers (ASTM-
D1238, G conditions) is 0.1 to 40 g/10 minutes, preferably 1 to 20 g/10 minutes. If it is less than 0.1 g/10 minutes, the melt viscosity of the resulting hot-melt pressure-sensitive adhesive composition will be high, making it impractical, and if it exceeds 40 g/10 minutes, the holding power will be low, which is undesirable. The styrene content in the block copolymer can be selected within the range of 5 to 50% by weight, preferably 10 to 45% by weight, based on the total polymer. Outside this range, the resulting adhesive tapes using the hot-melt adhesive will have poor adhesive properties, which is not preferred. Further, the block copolymer may be any one as long as it is represented by the above general formula, but
In particular, the block copolymer represented by (A-B) mA has a lower melt viscosity than that of block copolymers represented by other general formulas, and is difficult to process. It is advantageous and preferable from the viewpoint of performance. A modified product obtained by grafting an unsaturated carboxylic acid or a derivative thereof onto the above-mentioned block copolymer (hereinafter simply referred to as "modified block copolymer") can generally be obtained as follows. That is, examples of unsaturated carboxylic acids or derivatives thereof that can be grafted onto the block copolymer to form a modified block copolymer include maleic acid, fumaric acid, itaconic acid, acrylic acid, methacrylic acid, and crotonic acid. , cis-4-cyclohexene-
These include 1,2-dicarboxylic acid, endo-cis-bicyclo[2,2,1]-5-heptene-2,3-dicarboxylic acid, and derivatives of these carboxylic acids include acid anhydrides, esters, Examples include acid amides and dicarboxylic acid imides, among which dicarboxylic anhydrides are preferred, and maleic anhydride is particularly preferred. The content of unsaturated carboxylic acid or its derivative in the modified block copolymer of the present invention is from 0.01 to
30% by weight, preferably 0.05-10% by weight. If it is less than 0.01% by weight, there is almost no effect of improving the initial adhesion and retention force by grafting, and if it exceeds 30% by weight, the effect does not become large. The modified block copolymer of the present invention can be produced by combining the above block copolymer and an unsaturated carboxylic acid or a derivative thereof in a molten state or a solution state.
It can be obtained by grafting an unsaturated carboxylic acid or a derivative thereof onto the block copolymer, with or without the use of a radical initiator. Regarding the manufacturing method of these modified block copolymers,
Although not particularly limited in the present invention, production methods in which the obtained modified block copolymer contains undesirable components such as gel, or in which the melt viscosity thereof is greatly reduced and processability is deteriorated are not preferred. A preferred method is, for example, a method in which the above-mentioned block copolymer is grafted with an unsaturated carboxylic acid or a derivative thereof under melt-mixing conditions that substantially do not generate radicals in an extruder. Next, as the adhesive resin of the present invention, a polyterpene adhesive resin is used. With adhesive resins other than polyterpene-based resins (e.g., rosin-based resins, petroleum-based resins, phenol-based resins, styrene-based resins, xylene resins, coumaron-inten resins, etc.), the initial tackiness and retention of the resulting hot-melt adhesive may vary. The power is unbalanced and is of little practical use. The polyterpene adhesive resin is used in an amount of 50 to 200 parts by weight based on 100 parts by weight of the modified block copolymer.
Outside this range, the resulting hot-melt pressure-sensitive adhesive will have an unfavorable balance between initial tackiness and holding power. Examples of polyterpene resins include (co)polymers of α-pinene, β-pinene, and dipentene, and copolymers of these terpene hydrocarbons and phenols. Among these, α-pinene polymers are particularly popular. preferable. Next, the softener of the present invention is used in an amount of 5 to 200 parts by weight based on 100 parts by weight of the modified block copolymer. If it exceeds 200 parts by weight, the holding power of the resulting hot-melt adhesive will decrease, which is not preferable. Softeners include rubber extender oils (e.g. process oils), plasticizers (e.g. phthalate esters,
fumaric acid ester, phosphoric acid ester, etc.), liquid rubber (for example, liquid polybutadiene, etc.), etc. can be used. In addition, adhesive resins other than polyterpene-based resins (e.g., rosin-based resins, petroleum-based resins, phenol-based resins, styrene-based resins, xylene resins, coumaron-indene resins, etc.) are important for the initial tackiness and retention of hot-melt adhesives. It can be used additionally as long as the balance of power is not affected. Regular rubber (e.g. natural rubber, polyisoprene rubber, styrene)
Butadiene copolymer rubber, styrene-conjugated diene block copolymer, etc.) and fillers may be added as long as they do not impair the characteristics of the hot-melt adhesive. Furthermore, if desired, antioxidants, ultraviolet absorbers, colorants, etc. may be added. Various methods can be used to produce the hot-melt adhesive composition of the present invention. For example, a melting kettle, kneader, mixing roll, extruder, internal mixer, etc. can be used. The hot-melt pressure-sensitive adhesive composition of the present invention having an excellent balance between initial tackiness and holding power is extremely effective for various pressure-sensitive adhesive tapes, labels, and other pressure-sensitive products. Examples are shown below. The examples are representative of the invention but are not intended to limit the scope of the invention. Example 1 In a nitrogen gas atmosphere, n-butyllithium was added to a toluene solution containing styrene,
After styrene polymerization has started and more than 99% of the styrene has polymerized, a toluene solution containing 1,3-butadiene is further added, and after 99% or more of the added 1,3-butadiene has polymerized, the activity is activated. Silicon tetrachloride was added without loss, and a coupling reaction was performed. The obtained polymer was a (polystyrene-polybutadiene) ₄ -silicon block copolymer with a melt flow (G condition) of 8 g/10 minutes and a styrene content of 30% by weight. The above styrene-butadiene block copolymer
1.5 parts by weight of maleic anhydride per 100 parts by weight,
0.2 parts by weight of phenothiazine was added, and these were mixed uniformly using a mixer. This mixture was passed through a 40 m/m extruder (single screw, L/D = 24, full flight screw) under a nitrogen atmosphere.
The maleation reaction was carried out at a cylinder temperature of 200°C. After the reaction was completed, unreacted maleic anhydride was removed under reduced pressure. The obtained polymer had a melt flow index (G conditions) of 5.2,
The toluene insoluble content was 0.05% by weight, and the amount of maleic anhydride added was 0.70% by weight. Modified block copolymer obtained by the above method
For 100 parts by weight, add 100 parts by weight of YS resin A-1150 (α-vinene polymer, softening point 115°C, manufactured by Cheap Crude Oil) in a container with a stirrer, and Sonic Process Oil R-200.
(Nippon Mining Co., Ltd.) 50 parts by weight, Nokratsuku NS-7 (2,
3 parts by weight of 5-di-tert-butylhydroquinone (manufactured by Ouchi Shinko Kagaku) were charged and melted by heating at approximately 180°C. After melting, the modified block copolymer described above
100 parts by weight were added and melt mixing was continued for about 1 hour to obtain a clear, smoothly flowing, homogeneous composition. This composition was poured into a mold and cooled to form a sticky block. A portion of the hot-melt adhesive produced in this way was melted and applied to a thickness of approximately 50μ on kraft base paper (basis weight 75 g/m ² ) that had been back-treated at approximately 170°C. A tape was made. The initial tackiness (tack) and holding power to paper (flap holding power) of this kraft adhesive tape were measured, and the results are shown in Table 1. Each measurement was carried out by the method shown below. For the tack, adhesive tape is fixed on a board with an angle of 30°, and J.
Measure the ball number that stopped on the surface of the adhesive tape using Dow's ball rolling method. The higher the ball number, the greater the tack. Tack measurements were carried out at 20°C. As shown in Figure 1, the flap retention force is determined by attaching two sheets of corrugated paper (60 mm vertically, 50 mm horizontally, 5 mm thick) 3, spaced 2 mm apart in the center of two sheets of corrugated paper (width 20 mm, length 27 mm), facing each other in the vertical direction. Adhesive tape 4, weight
The corrugated paperboards 3 and 4 to which the adhesive tape was attached by pressing twice using a 200 g roller were fixed to the iron plate flap 2, and a 1 kg load 5 was applied between the gap in the center of the iron plate flap 2. ,40℃
The time taken for the adhesive tape to peel off was measured under the following temperature conditions. Examples 2 to 5 Table 1 shows the results obtained by using the same method as in Example 1 and using the formulations shown in Table 1. Comparative Example 1 In Example 1, the modified block copolymer was
Table 1 shows the results of using the formulation shown in Table 1 using the same method except for using a styrene-butadiene block copolymer before modification. Comparative Examples 2 to 5 Table 1 shows the results obtained by using the same method as in Example 1 and using the formulations shown in Table 1. As is clear from Table 1, the hot-melt adhesive of the present invention has an extremely excellent balance between initial tackiness and holding power.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a side view showing a method for measuring flap retention force. 1 is a fulcrum, 2 is a steel flap, 3 is cardboard, 4 is adhesive tape, and 5 is a weight.

Claims (1)

[Claims] 1 General formula A-B-A, (AB) _o , B(-A-B)
_o , (A-B)-nA, (A-B)mX [where B is substantially polybutadiene or polyisoprene block, A is substantially polystyrene block,
n represents an integer from 2 to 10. X is a polyfunctional compound to which m polymer chains are bonded, m is 3 to
Represents the integer 7. ] The flow rate (ASTM-D1238, G conditions) is in the range of 0.1 to 40 g/10 min, and the styrene content is in the range of 5 to 50% by weight. Saturated carboxylic acid or its derivative from 0.01
A heat melting product comprising a modified material grafted in an amount of 30% by weight, and 20 to 200 parts by weight of a polyterpene adhesive resin and 5 to 200 parts by weight of a softener per 100 parts by weight of the modified material. Type adhesive composition.