JPH0598130A - Hydrogenated block copolymer composition and its hot-melt tacky adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition useful as a hot-melt tacky adhesive by compounding a hydrogenated block copolymer composed mainly of plural numbers of two specific kinds of compounds and a hydrogenated block polymer composed mainly of two specific kinds of compounds at a specific ratio. CONSTITUTION:The objective composition is composed of (A) a hydrogenated block copolymer produced by hydrogenating a high-molecular weight block copolymer containing (i) polymer blocks composed of two or more vinyl aromatic compounds and (ii) polymer blocks composed of two or more conjugated diene compounds (a block copolymer having a structure of i-ii-i-ii or longer) and having the component (ii) as a polymer chain terminal and (B) a hydrogenated block polymer produced by hydrogenating a low-molecular weight block copolymer containing (i) a polymer block composed of one or more vinyl aromatic compounds and (ii) a polymer block composed of one or more conjugated diene compounds (a block copolymer having i-ii structure) and having the component (ii) as a polymer chain terminal. The content of the component (i) in each of the component A and B is 25-40wt.%, the ratio of A:B is 80:20 to 20:80, the average molecular weight of the components A and B is 20,000-80,000 and the molecular weight ratio of the component A to the component B is 1.5-4.5.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrogenated block copolymer composition having a specific structure and an adhesive composition thereof. The composition of the present invention has a low melt viscosity required for a hot-melt type pressure-sensitive adhesive, excellent adhesive properties (tack, peel strength, holding power) and heat stability, and is a sanitary material such as a disposable diaper and a sanitary napkin. It is effective as an adhesive material in the field of.

[0002]

2. Description of the Related Art Conventionally, pressure sensitive adhesives have been used for various purposes such as pressure sensitive adhesive tapes and labels. The adhesive is generally applied to these tapes by applying an adhesive solution obtained by dissolving the adhesive in a solvent to a substrate by means of rolls, sprays or the like. However, the use of such a solvent has many problems from the viewpoint of air pollution, fire, hygiene, etc., and it is becoming a serious social problem. Therefore, as a means for solving such inconvenience,
Non-solvent type hot melt type adhesives have been attracting attention.

[0003] Among hot-mel type adhesives, the one that is currently growing very much is the use as an adhesive in the hygiene-related market such as paper diapers and napkins. A special requirement for such hot melt adhesives is that they have excellent coating stability. For this purpose, good fluidity is required. (Low melt viscosity) Good adhesive property. (Tack, peel strength, holding power) No change in viscosity or coloring due to heating. (Thermal stability) and the like.

Recently, there has been a demand for a hot-melt type pressure-sensitive adhesive having a lower melt viscosity in order to improve the processability. However, if the viscosity is lowered, the problem is that the essential pressure-sensitive adhesive properties are deteriorated. There is a point. Therefore, it is desired to develop a hot-melt pressure-sensitive adhesive having a viscosity lower than that of the conventional hot-melt pressure-sensitive adhesive and having excellent adhesive properties. The reality is that there is no excellent product that satisfies all of the above.

For example, JP-B-44-17037 and JP-B-47-21720 disclose hot-melt type pressure-sensitive adhesives using a block copolymer composed of styrene-butadiene-styrene or styrene-isoprene-butadiene. ing. However, although they have excellent adhesive strength, they are severely deteriorated by heating and cannot be used in such an environment. To improve that point,
A pressure-sensitive adhesive obtained by hydrogenating a conjugated diene moiety to form a styrene-ethylene / butylene-styrene block copolymer is disclosed in U.S. Pat. No. 3,427,269 and JP-B-55-7875.

However, the addition of hydrogen also significantly reduces the adhesive strength and the melt viscosity at high temperature is high, and the use thereof is extremely limited. Others, US Patent No. 4
286077 discloses an example using a low styrene-containing multiblock copolymer or a low styrene diblock copolymer as a hydrogenated block copolymer. However, although this also has a low melt viscosity, the holding power is remarkably reduced and the performance is insufficient. Also,
Japanese Patent Application Laid-Open No. 2-1788 also discloses, as a hydrogenated block copolymer, a combination of a triblock structure and a block copolymer having a specific structure. However, the compositions disclosed herein also have an insufficient balance of melt viscosity and tack.

As described above, no hot-melt type pressure-sensitive adhesive which satisfies all the above-mentioned required characteristics has been found so far, and the present situation is to use it while having various problems. In particular, there is a demand for the development of a hot melt type pressure-sensitive adhesive having a low melt viscosity, excellent coating stability, and excellent adhesive properties.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a hydrogenation block suitable for an adhesive used for a paper diaper, a napkin, etc., which has an excellent adhesive property even though it has a low melt viscosity and has a good thermal stability. It is intended to provide a copolymer composition and a hot-melt pressure-sensitive adhesive composition containing the same.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have made earnest studies on the correlation between the polymer structure of a hydrogenated product of a vinyl aromatic compound block-conjugated diene compound block copolymer and its adhesive property. As a result, the hydrogenated block copolymer having a specific structure has a very low melt viscosity,
It was found that the pressure-sensitive adhesive composition has excellent processability and pressure-sensitive adhesive properties, and has completed the present invention.

That is, the present invention comprises (a) a polymer block A mainly containing at least two vinyl aromatic compounds and a polymer block B mainly containing at least two conjugated diene compounds, and at least 1 Polymer block B is mainly composed of a hydrogenated block copolymer obtained by hydrogenating a high molecular weight block copolymer having a polymer chain at the end thereof, and (b) at least one vinyl aromatic compound. Hydrogenating a low molecular weight block copolymer having a polymer block C and at least one polymer block D mainly composed of a conjugated diene compound, and at least one polymer block D being at the end of a polymer chain. And a vinyl aromatic compound content of each of (a) and (b) is 2 or more.
5-40% by weight, and the ratio of (a) and (b) is 80/20 to 20/8.
0, the average molecular weight (Mn) of (a) and (b) is 20,000
˜80,000, molecular weight ratio of (a) and (b) (Mn of (a) / M of (b))
A hydrogenated block copolymer composition having n) of 1.5 to 4.5, and a hot-melt pressure-sensitive adhesive composition containing the hydrogenated block copolymer composition.

The main features of the present invention are a copolymer obtained by hydrogenating a high molecular weight block copolymer in which the polymer chain end is a conjugated diene block, and a low molecular weight block in which the polymer chain end is a conjugated diene block. Both of the copolymers obtained by hydrogenating the copolymers are used, and the average molecular weight and the molecular weight ratio thereof are defined in a specific range. With such a structure, when used as an adhesive composition, a hot melt type adhesive composition having a low melt viscosity and excellent adhesive properties was obtained.

The present invention will be described in detail below. The hydrogenated block copolymer of the present invention has a microstructure such as the structures of the high molecular weight block copolymer (a) and the low molecular weight block copolymer (b), the vinyl aromatic compound amount and the vinyl bond amount before hydrogenation. , They may be the same or different,
It does not matter if it is within the above range.

The polymer block A or C mainly containing a vinyl aromatic compound has a weight ratio of the vinyl aromatic compound and the conjugated diene compound of 100/0 to 51/49, preferably 100/0 to 70/30. When the vinyl aromatic compound and the conjugated diene compound are copolymerized, the distribution of the conjugated diene compound in this block is random or tapered (the monomer component increases or decreases along the molecular chain). ), Partially block-shaped, or any combination thereof.

In the polymer block B or D containing a conjugated diene compound as a main component, the weight ratio of the vinyl aromatic compound to the conjugated diene compound is 0/100 to 49/51, preferably 0/100 to 30/70. When the conjugated diene compound and the vinyl aromatic compound are copolymerized, the distribution of the vinyl aromatic compound in this block is random or tapered (the monomer component increases along the molecular chain or Decrease), partial block, or any combination thereof.

The vinyl aromatic compound provided here is one or two of styrene, alkylstyrene such as α-methylstyrene, p-methylstyrene and p-tertiarybutylstyrene, paramethoxystyrene, vinylnaphthalene and the like. More than one species are selected, among them styrene, p
-Methylstyrene is particularly preferred. Further, as the conjugated diene compound, butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,
One or more kinds are selected from 3-octadiene and the like, and among them, butadiene and / or isoprene are particularly preferable.

The content of vinyl aromatic compound is 25-4.
The range of 0 wt% is preferable, and the range of 25 to 35 wt% is more preferable. When the content of the vinyl aromatic compound exceeds 40% by weight, the tack of the pressure-sensitive adhesive composition is lowered and the melt viscosity is increased. On the other hand, if it is less than 25%, the holding force and the creep property will be insufficient.

The microstructure of the conjugated diene portion is preferably such that the vinyl bond content before hydrogenation is in the range of 30 to 70%, and 40 to 40%.
The range of 60% is more preferable, and the range of 50 to 60% is further preferable. (The vinyl bond content is 1,2-bond, 3,4-bond, or 1,2-bonded diene compounds incorporated in the 1,4-bond bonding mode in the block copolymer.
If the vinyl bond content is less than 30%, the melt viscosity is insufficient, and if it exceeds 70%,
The tackiness of the obtained pressure-sensitive adhesive composition decreases. The microstructure of the conjugated diene portion can be analyzed by an infrared spectrophotometer (IR), a nuclear magnetic resonance apparatus (NMR) or the like.

The hydrogenated block copolymer of the present invention is
(A) a high molecular weight and (b) a low molecular weight hydrogenated block copolymer, and the ratio of (a) / (b) is from 80/20.
It is necessary to be 20/80 (% by weight). And the total number average molecular weight is 20,000 to 80,000.
Mn of the molecular weight ratio (a) of (a) and (b)
If the Mn of / (b) is in the range of 1.5 to 4.5, there is no particular restriction.

The total number average molecular weight referred to here is
It is the average molecular weight of (a) and (b), and the individual number average molecular weight can be measured by gel permeation chromatography (GPC) by a conventional method. In the production method, for example, the high molecular weight hydrogenated block copolymer and the low molecular weight hydrogenated block copolymer may be separately produced and blended. In addition, during the polymerization, a polymerization catalyst may be additionally added (sequential polymerization method by catalyst division) to produce a mixture of block copolymers having different molecular weights, and then hydrogenated. Further, a low molecular weight block copolymer may be subjected to a coupling reaction, the coupling rate may be controlled within the above range, and then hydrogenated for production.
Whichever method is used, it is sufficient if it has the structure of the present invention.

In the case of the pressure-sensitive adhesive composition, if the proportion of (a) exceeds 80% by weight, the melt viscosity is high and the tack is lowered, which is not preferable. On the other hand, if the proportion of (b) exceeds 80% by weight, the holding power will be lowered and sufficient adhesive properties cannot be obtained. Further, when the total average molecular weight exceeds 80,000, the melt viscosity increases remarkably and it becomes difficult to use as a hot melt type pressure-sensitive adhesive, and when it is less than 20,000, sufficient holding power cannot be obtained.

The molecular structure of the block copolymer may be linear, branched, radial or a combination thereof. And, each of the polymer block mainly composed of vinyl aromatic compound or the block mainly composed of conjugated diene may have the same structure, the content of the monomer component, the distribution in their molecular chains, and the molecular weight of the block. Each structure such as a micro structure may be different.

The block copolymer can be produced by, for example, Japanese Patent Publication No. 36-19286 and Japanese Patent Publication No. 43-149.
79, Japanese Patent Publication No. 49-36957 and the like. In these, an organic lithium compound or the like is used as an anionic polymerization initiator in a hydrocarbon solvent, an ether compound such as diethyl ether or tetrahydrofuran as a vinylating agent, triethylamine, N,
Tertiary amines such as N, N ′, N′-tetramethylethylenediamine and, if necessary, polyfunctional compounds such as epoxidized soybean oil, diethyl carbonate and silicon tetrachloride as coupling agents, and vinyl aromatic compounds It is a method of block copolymerizing a conjugated diene compound, and is obtained as a block copolymer having a linear, branched or radial structure. In the present invention, any polymer obtained by any polymerization method can be used as long as it is as described above.

The above block copolymer is prepared by a known method,
For example, a hydrogenated block copolymer can be obtained by hydrogenating according to the method described in JP-B-42-8704. The present invention requires 80% or more of the conjugated diene moieties to be hydrogenated. When the hydrogenation rate is low, the thermal stability is poor. That is, a change in viscosity occurs due to heating, resulting in deterioration of characteristics and a change in color tone. The hydrogenation rate can be analyzed by an instrumental analysis using an infrared spectrophotometer (IR), a nuclear magnetic resonance apparatus (NMR) or the like, a titration analysis by an iodometric titration method or the like.

The hydrogenated block copolymer used in the present invention may be modified by an addition reaction with an unsaturated carboxylic acid or a derivative thereof to contain a functional group.
The hydrogenated block copolymer composition of the present invention contains an adhesive resin, a softening agent, and optionally other compounding agents,
Used as an adhesive composition.

The adhesive resin has been conventionally used as a tackifier in hot-melt type adhesives, and includes, for example, coumarone indene resin, phenol resin, p-tertiary-butylphenol / acetylene resin, phenol.
Formaldehyde resin, terpene / phenolic resin, polyterpene resin, xylene / formaldehyde resin, synthetic polyterpene resin, aromatic hydrocarbon resin, aliphatic cyclic hydrocarbon resin, oligomer of monoolefin and diolefin, hydrogenated hydrocarbon resin, carbonization Hydrogen-based tackifying resin, polybutene, polyhydric alcohol ester of rosin, hydrogenated terbene resin, hydrogenated rosin, hydrogenated wood rosin, ester of hydrogenated rosin and monoalcohol or polyhydric alcohol, turpentine tackifier, etc. Be done.

More specifically, those described in "Rubber-Plastic Blended Chemicals" (edited by Rubber Digest) can be used. In the present invention, the adhesive resin is generally 40 to 4 with respect to 100 parts by weight of the hydrogenated block copolymer.
Used in the range of 00 parts by weight.

The softening agent is a petroleum-based softening agent, paraffin, vegetable oil-based softening agent, plasticizer, etc. Specifically, the softening agents described in the above-mentioned "rubber / plastic compounding chemicals" can be used. The softening agent is generally used in the range of 20 to 200 parts by weight based on 100 parts by weight of the hydrogenated block copolymer. Other additives such as antioxidants and ultraviolet absorbers may be added in an amount of 10 parts by weight or less relative to 100 parts by weight of the block copolymer to further improve weather resistance, heat resistance and oxidation resistance. Powder fillers such as calcium and titanium oxide, fibrous fillers such as glass fibers and organic reinforcing fibers may be mixed.

The hydrogenated block copolymer composition of the present invention is made into a hot-melt type pressure-sensitive adhesive composition by, for example, putting the above-mentioned raw materials in a melt-stirring mixing vessel and heating and mixing. The hot-melt type pressure-sensitive adhesive composition is effective as a pressure-sensitive adhesive for various sheets and tapes and can be used particularly in the field of sanitary materials such as paper diapers and sanitary napkins, and has an extremely great industrial utility value.

[0029]

EXAMPLES In order to describe the present invention more specifically, examples will be shown below, but the present invention is not limited to these examples.

(I) Preparation of Hydrogenated Block Copolymer (1) Anion block copolymerization of styrene and butadiene with n-butyllithium as a polymerization catalyst and tetrahydrofuran as a vinyl content modifier in a cyclohexane solution. Thus, the block copolymers shown in Table 1 were synthesized. The polymer structure was controlled by changing the charged amount of monomers, the molecular weight of the catalyst, and the vinyl content of the vinyl content modifier.

With respect to c-1 to c-7, polymerization was carried out by a sequential polymerization method with catalyst division. For example, (c
In -1), a catalyst was additionally added during the polymerization of the third butadiene monomer to further promote the polymerization. The styrene content was measured by an ultraviolet spectrophotometer (UV), the vinyl content was measured by an infrared spectrophotometer (IR), and the number average molecular weight was measured by gel permeation chromatography.

(2) Next, each block copolymer was hydrogenated at a hydrogen pressure of 70 kg / cm ² and a temperature of 50 ° C. for 8 hours using cobalt naphthenate and triethylaluminum as catalysts. The hydrogenation rate (hydrogenation rate) of each sample is shown in the right column of Table 1. 90 of double bonds in butadiene block
% Or more was hydrogenated, and the benzene ring in the styrene block portion remained with almost no hydrogenation. Note that c-5 is c
It is the same polymer as -4, but without hydrogenation reaction. Hydrogenation rate is measured by nuclear magnetic resonance (NMR)
Was measured.

(II) Preparation of pressure-sensitive adhesive composition and evaluation of respective properties Block copolymers shown in Table 1 and pressure-sensitive adhesive resins, softening agents,
The antioxidants were blended as shown in Tables 2 and 4 and melt-mixed using a kneader to prepare a hot-melt type pressure-sensitive adhesive. The following characteristics were measured using the obtained pressure-sensitive adhesive, and the results are shown in Tables 3 and 5.

Melt viscosity The pressure-sensitive adhesive composition was measured for melt viscosity at 180 ° C. using a Brookfield viscometer. (Number of revolutions:
100 rpm, rotor: No. 21).

Loop tack Using a loop-shaped sample of 250 mm × 15 mm width,
The adherend was a polyethylene sheet, and the adhesive strength was measured under the following conditions. (Adhesion area: 15 mm x 50 mm, adhesion time: 3 sec, adhesion and peeling speed: 500 mm /
sec).

Peel strength A sample having a width of 25 mm was attached to a polyethylene sheet and the 180 ° peel force was measured. (Peeling speed: 30
0 mm / min).

Holding power: 1k for a bonded part having an adhesive area of 25 mm × 25 mm
A load of g was applied, the mixture was left at 60 ° C., and the time until it dropped was measured.

Thermal stability It was left for 144 hours in a temperature atmosphere of 180 ° C., the viscosity before and after that was measured, and the change in viscosity before and after that was determined and used as an index of thermal stability. ⊚: Viscosity change rate is less than 10% ◯: Viscosity change rate is 10% to 20% Δ: Viscosity change rate is 20% to 50% ×: Viscosity change rate is 50% or more Viscosity change rate = V−V ₀ / V ₀ × 100 (%) (V: Melt viscosity after heat history (180 ° C., 144 hours)) (V ₀ : Melt viscosity before heat history).

Examples 1 to 4 Each of the high molecular weight hydrogenated block copolymers (a) shown in Table 2 and the low molecular weight hydrogenated block copolymers (b) were blended, and the tackiness to 100 parts by weight was blended. 300 parts by weight of Clearon P-105 (made by Yasuhara) as a resin, 100 parts by weight of PW-90 (made by Idemitsu Kosan) as a softening agent, and 1 part by weight of Irganox 1010 (made by Ciba Geigy) as an antioxidant. Was blended in to prepare each pressure-sensitive adhesive composition at 180 ° C., and the results are shown in Table 3. These were pressure-sensitive adhesive compositions having a low melt viscosity, an excellent balance of loop tack, peel strength, and holding power, and an excellent thermal stability.

Examples 5 to 8 Similar to Examples 1 to 4, Examples 5 to 8 were carried out using block copolymers which were polymerized by the sequential polymerization method by catalyst division. It can be seen that excellent characteristics are exhibited as in Examples 1 to 4.

The above-mentioned examples are all examples of compositions included in the constitution of the present invention, and have low melt viscosity suitable for hot-melt type adhesives, excellent adhesive property and thermal stability. Is. The superiority of the characteristics will become more apparent by comparing with the following comparative examples. Also, the effect of defining the structure is clear.

Comparative Examples 1 to 3 are examples in which the ratio of the high molecular weight hydrogenated block copolymer (a) to the low molecular weight block copolymer was outside the range of the present invention. It can be seen that the balance between melt viscosity and adhesive properties is poor.

Comparative Examples 4 and 5 In this example, the block copolymer has a triblock structure. It can be seen that the melt viscosity and tack are poor.

Comparative Example 6 This is an example using the same base polymer as in Example 6 of the present invention, but using a non-hydrogenated block copolymer (c-5). The thermal stability is remarkably inferior and the holding power is also inferior.

Comparative Example 7 The vinyl aromatic compound of the hydrogenated block copolymer is an example outside the scope of the present invention. It can be seen that the holding power is extremely poor. The importance of the vinyl aromatic compound content in the hydrogenated block copolymer is understood.

Comparative Example 8 This is an example when the average molecular weight is too high. It can be seen that the melt viscosity of the pressure-sensitive adhesive composition is high and the tack is significantly inferior.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[0052]

INDUSTRIAL APPLICABILITY The present invention is a hydrogenated block copolymer composition having a specific structure and a hot-melt type pressure-sensitive adhesive composition containing the same, which has a low melt viscosity and is suitable for a hot-melt type pressure-sensitive adhesive. It has the effect of having adhesive properties (tack, peel strength, holding power) and thermal stability.

Claims (2)

[Claims] 1. A method comprising: (a) a polymer block A mainly containing at least two vinyl aromatic compounds and a polymer block B mainly containing at least two conjugated diene compounds, and at least one polymer block A hydrogenated block copolymer obtained by hydrogenating a high molecular weight block copolymer having a polymer block B at the end of a polymer chain, and (b) a polymer block mainly containing at least one vinyl aromatic compound Obtained by hydrogenating a low molecular weight block copolymer having a polymer block D mainly composed of C and at least one conjugated diene compound, and having at least one polymer block D at the end of a polymer chain. And a vinyl aromatic compound content of each of (a) and (b) is 2
5 to 40% by weight, and the ratio of (a) and (b) is 80/20 to 20/8.
0, the average molecular weight (Mn) of (a) and (b) is 20,000
˜80,000, molecular weight ratio of (a) and (b) (Mn of (a) / M of (b))
A hydrogenated block copolymer composition in which n) is 1.5 to 4.5. 2. A hot-melt pressure-sensitive adhesive composition containing the hydrogenated block copolymer composition according to claim 1.