JPS58476B2 - hot melt adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot melt adhesive composition containing a novel butanediene-styrene-α-methylstyrene copolymer.

More specifically, the present invention relates to a hot-melt adhesive composition that has high adhesive ability, low melt viscosity, and good heat resistance and cold resistance.

Various types of hot-melt adhesives have been proposed in the past, with the most common being a mixture of ethylene-vinyl acetate polymer and rosin or wax, but recently butadiene-styrene block copolymers have also been used for this purpose. Therefore, there are examples of using paraffin wax, petroleum-based hydrocarbon resin, etc. as coarse gold.

However, this composition has a high melt viscosity and therefore a low adhesive ability, resulting in a decrease in workability.Also, it is not satisfactory in terms of heat resistance and cold resistance, and does not have desirable properties at the same time when used industrially. Not yet.

As a result of intensive research from this perspective, the present inventors have developed various hot-melt adhesive compositions consisting of a homogeneous mixture of a butadiene-styrene-α-methylstyrene block copolymer, a wax, an adhesive resin, and a stabilizer. The present invention has been accomplished by discovering that an adhesive composition can be obtained which has strong adhesion ability to adherends, has excellent heat resistance and cold resistance, and has a low melt viscosity.

That is, the present invention provides a hot melt adhesive composition that has excellent heat resistance and cold resistance, and has a low melt viscosity.

The hot melt adhesive composition of the present invention comprises (1) butadiene-styrene-α-methylstyrene block copolymer 10-8
0 parts by weight, (2) 30 to 90 parts by weight of wax, (3) 50 to 160 parts by weight of adhesive resin, and (4) 0.5 to 2 parts by weight of stabilizer. However, the melt viscosity is small (the melt viscosity at 150° C. is 30,000 to 4,500 centipoise).

), it has excellent workability and good heat resistance and cold resistance, so it is preferably used for many adherends.

Butadiene-styrene-α- used in the present invention
Methylstyrene block copolymer is a conjugated diene (e.g. isoprene, 1,3-butadiene, etc.) using an alkali metal compound as an initiator: a vinyl-substituted aromatic hydrocarbon (e.g. styrene,
A block copolymer obtained by copolymerizing three components: (3-vinyltoluene, etc.):B α-methylstyrene:C,
For example, the block copolymer has a structure of (A-C)n n=1 or more (A-C-B)n B-C-B-A-B-C-B, and the block copolymer also includes a part of the taper. Block letters are also included in this range.

The taper refers to a portion where the copolymerization ratio of styrene and butadiene changes continuously along the polymerization chain.

The composition of each component is A: 30 to 80% by weight, preferably 50% by weight.
-70% by weight, B+C: 70 to 20% by weight, and if B is more than 5% by weight and less than 5% by weight, it will not meet the purpose of the present invention.

The molecular weight of the copolymer is preferably 20,000 to 200,000, preferably 30,000 to 150,000.

If the adhesive is below this range, the cohesive force of the adhesive will be weak, and if it exceeds the above range, the melt viscosity will be insufficient, and in either case, the adhesive ability will be insufficient.

By using the butadiene-styrene-α-methylstyrene block copolymer of the present invention in a hot-melt adhesive composition, the melt viscosity is significantly lower than that of conventional butadiene-styrene block copolymers, and the heat resistance is improved. We can also expect an improvement in

Formula % Formula %) ) (However, A is a conjugated diene, B is a vinyl-substituted aromatic hydrocarbon, C is α-methylstyrene, and n=1 or more.

) A living anionic polymerization method is usually used to produce the block copolymer.

That is, using an alkyl metal compound represented by the general formulas R1-X and X-R2-X as a catalyst,
Alkyl groups such as butyl, 5ec-butyl, t-butyl,
R2 is an oligomer such as butadiene, styrene, α-methylstyrene, etc.; X is an alkali metal such as lithium or sodium; It is obtained by sequentially adding monomers and polymerizing them.

Furthermore, it is necessary to polymerize α-methylstyrene under low temperature conditions (-80 to +5°C) in order to reduce the equilibrium monomer concentration, and hexamethylene phosphoramide or the like is added as a polymerization activator.

An example of a method for industrially advantageous polymerization is disclosed in Japanese Patent Application No. 47-97768.

In addition to hydrocarbons such as paraffin wax, microcrystalline wax, and polyethylene Fuchs, waxes used in the present invention include halogenated high molecular weight hydrocarbons such as chlorinated paraffin wax, oxidized paraffin wax, and maleated paraffin wax. Also mentioned are modified high molecular weight hydrocarbons.

The type of wax used is not limited to one type; for example, a combination of ordinary paraffin wax and microcrystalline wax can also give favorable results on the adhesive surface.

If the amount of wax used is less than 30 parts by weight, the melt viscosity will increase, and if it is more than 90 parts by weight, the adhesiveness will decrease.

A range of 30 to 90 parts by weight is suitable.

In addition to naturally occurring rosins, the adhesive resin used in the present invention includes synthetic rosin-like compounds such as terpene resins, petroleum resins, indencoumarone resins, and xylene-formalin resins, and hydrogenated rosins. , those esterified with glycerin, glycols, etc.
Those modified with formaldehyde, amines or unsaturated acids such as maleic acid can also be preferably used.

These adhesive resins are not limited to one type, but may be used in combination of two or more types. Preferably, petroleum resin (Betaprene H-100 manufactured by Reichhold Chemical Co., Ltd.) and indencoumarone resin (Pico N100 manufactured by Pencil Venia Industrial Chemical Co., Ltd.) are used. A combination is used.

This provides the adhesive composition of the present invention with extremely good tack and fluidity, and increases the wetting of the adherend, thereby significantly increasing the adhesion ability.

If the amount of the adhesive resin used is less than 50 parts by weight, the wetting effect will be poor, and if it is more than 160 parts by weight, the adhesiveness will decrease.

A range of 50 to 160 parts by weight is suitable.

Stabilizers used in the present invention include those that can be used in conventional butadiene-styrene block copolymers, such as Ionox 330 (manufactured by Shell) and Irganox 1076.1010°565 (manufactured by Ciba and Geigy). It will be done.

The amount of stabilizer used is 2 parts by weight or less, and 0.5 to 2 parts by weight is sufficient.

When the composition of the present invention is applied to wood, plastic, metal, etc. and then heated and melted, it exhibits excellent adhesion to various substrates, and its strength is fully comparable to that of commercially available compositions.

The adhesive composition in the present invention is made by thermally melting the four or five components described above.

That is, it is obtained by uniformly heating and mixing the above-mentioned components at 180 to 190°C.

The composition thus obtained becomes fluid when heated to around 160°C, and in that state is applied to the adhesive surface and bonded under pressure.

EXAMPLES The salient points of the present invention will be shown below by way of Examples, but the scope of the present invention is not limited thereby.

The peel strength and shear strength tests in the examples were conducted by applying an adhesive to the adherend surface, leaving the adhesive layer under pressure at room temperature for 2 days, leaving it at the measurement temperature for 1 to 2 hours, and conducting a Finstron tensile test at a tensile rate of 5.
The strength was measured at 0 mm/min, and the melt viscosity was measured using a B-type viscometer.

Production method of block copolymer (formulation of examples) In a nitrogen gas atmosphere, put 11 purified dehydrated benzene and 5 g of styrene into a glass flask equipped with a stirrer, and then add 13 g of butadiene.
4 g of butadiene oligomer dilithium was added as a polymerization initiator, and polymerization was carried out at 50° C. for 2 hours.

After the polymerization of butadiene was completed, the polymerization system developed a red color, and the polymerization of styrene continued and completed.

At this stage, a pasting polymer with a B-A-B structure is formed.

Subsequently, after adding 2 ml of hexamethylene phosphoramide, the reactor was cooled to 5°C, and 4 ml of α-methylstyrene was added.
6 g was added and polymerized for 10 minutes.

Subsequently, 15 g of styrene was continuously added little by little for about 1 hour to complete the polymerization.

The polymer was recovered from the obtained polymer solution by a steam stripping method.

The yield was 99%. The number average molecular weight determined by osmometry was 120,000.

Example 43 parts by weight of paraffin with a softening point of 68°C, Betaprene H
B- C-B -A-B-C-B A: Butadiene B: Styrene C: α-methylstyrene structure, A is 67%, B+C is 33% (B is 10%)
%) and 1 part by weight of Ionox 330 (manufactured by Shell) were added.
When heated and stirred at ~190°C, a pale brown transparent viscous substance was obtained.

The melt viscosity was 4000 centiponds/150°C.

Next, this is taken out from the container and formed into granules or rods as required.

As for the bonding method, the plastic film is melted at a temperature of 150 to 160 DEG C., and the plastic film is applied to a metal piece, and then another piece is bonded under heat and pressure at 100 DEG C. and 2 to 5 kg/cm@2.

Table 1 shows the peel strength and shear strength measured under conditions of a temperature of 20° C. and a relative humidity of 65%.

As a comparative example, butadiene-styrene block copolymer (
Table 1 shows the results of the same melt viscosity and strength tests for an adhesive with the same composition as the butadiene-styrene-α-methylstyrene block copolymer (molecular weight 100,000). Also shown in

Furthermore, Table 2 shows the peel strength of the polyester films at various temperatures, which was conducted according to the above-mentioned peel test.

Comparative Example 1 Butadiene-styrene- of Example 67% butadiene, styrene + α-methylstyrene 33% (of which B is 10%)
Instead of the α-methylstyrene block copolymer, 85% butadiene styrene + 15% α-methylstyrene (of which B is 10%) (manufacturing method is the same as in the example) 50 parts by weight 43 parts by weight of paraffin with a softening point of 68°C; Betaprene H-10
055 parts by weight, Pico N10020 parts by weight, and Ionox 3301 parts by weight were prepared in the same manner as in the following examples, and the adhesive strength was tested in the same test method as in the examples. As a result, the peel strength was 1 between polyester films. .2k
g/25mm shear strength is 17kg/25mm between stainless steel plates.
cm, and the peel strength between the polyester films at 50° C. was 0.3 kg/25 mm, which was a significant decrease in strength.

Comparative Example 2 Butadiene-styrene- with 67% of butadiene and 33% of styrene + α-methylstyrene (of which B is 10%)
Instead of α-methylstyrene block copolymer, 20% butadiene styrene + 80% α-methylstyrene (of which B is 10%) (manufacturing method is the same as in the example) 50 parts by weight, 43 parts by weight of paraffin with a softening point of 68°C , betaprene H-1
An adhesive was prepared in the same manner as in the examples below using 0055 parts by weight, 10020 parts by weight of Pico N, and 3301 parts by weight of Ionox, and as a result of testing in the same test method as in the examples, the melt viscosity increased to 25,000 centipoise. , Peel strength is 1.5kg/25 between polyester films
mm, shear strength between stainless steel plates is 19kg/cm2
Moreover, the peel strength between the polyester films at 50° C. was 0.4 kg/25 mm, which was a significant decrease.

Claims (1)

[Claims] 1(1) Formula % Formula %) ) (However, A is a conjugated diene, B is a vinyl-substituted aromatic hydrocarbon, C is α-methylstyrene, and n is an integer of 1 or more. ) A block copolymer of one or more selected types, whose composition is 30 to 80% by weight for A and 70% for B and C.
-20% by weight, of which B is 5% by weight or more, and 10-80 parts by weight of a block copolymer with an average molecular weight of 20,000-200,000 (2) 30-90 parts by weight of paraffin wax (3
) A hot-melt adhesive composition comprising 50 to 160 parts by weight of an adhesive resin (4) 0.5 to 2 parts by weight of a stabilizer.