JP3361547B2 - Hot melt adhesive - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention relates to a disposable diaper,
The present invention relates to a hot melt adhesive suitable for use in manufacturing sanitary napkins, bed pads and the like.

[0002]

2. Description of the Related Art As a hot-melt adhesive of this type, JP-A-60-158284 discloses an inelastic block having a glass transition point of 20 ° C. or higher, such as polystyrene block, and an elastic block such as polybutadiene block. A hot melt adhesive containing a linear (linear) type thermoplastic block copolymer comprising a hydrogenated polybutadiene block as a base polymer is disclosed.

Further, JP-A-2-145671 discloses a hot melt containing as a base polymer a radial type thermoplastic block copolymer comprising a polystyrene block and a polybutadiene block or a hydrogenated polybutadiene block. Adhesives are disclosed.

As described above, the hot melt adhesive containing the linear type or radial type thermoplastic block copolymer as the base polymer has particularly good adhesiveness to polyolefin such as polyethylene and polypropylene, and also has cohesive force. Good, transparent, and flexible and durable.

Therefore, this kind of hot melt adhesive mainly uses a polyolefin film or a non-woven fabric having a large number of fine ventilation holes, and is formed by adhering the polyolefin film or the non-woven fabric in a streak-like or dot-like manner. It is used in the manufacture of napkins and bed pads.

[0006]

However, since the adhesive is applied in stripes or dots in such applications, higher cohesive force and adhesive force are required, and the above-mentioned conventional linear Hot melt adhesives containing thermoplastic block copolymers of the type or radial type are not yet fully satisfactory in this respect and there is room for improvement.

That is, when a high molecular weight thermoplastic block copolymer is used as the base polymer in order to exhibit a high cohesive force, the melt viscosity is inevitably increased, and the workability of applying the adhesive is deteriorated.

Further, since the use temperature of the adhesive becomes high,
There is a problem that the polyolefin film or the non-woven fabric is deformed by heat, or the adhesive is thermally deteriorated to change the melt viscosity, so that the adhesive performance is deteriorated.

Incidentally, when the melt viscosity is lowered by adjusting the molecular weight of the thermoplastic block copolymer, not only the cohesive force is lowered, but also the adhesive component exudes from many fine vent holes of the polyolefin film or the nonwoven fabric. There is also. Also, the thermal stability is not sufficient.

The present invention is intended to solve the above problems, and its object is to have a high cohesive force and an adhesive force, a low melt viscosity, and a coating operation even when used at a relatively low temperature. It is an object of the present invention to provide a hot melt adhesive that has good properties, does not exude the adhesive component from the air holes of the adherend, and has good thermal stability.

[0011]

In order to achieve the above object, the hot melt adhesive of the present invention comprises an inelastic block having a glass transition point of 20 ° C. or higher and an elastic block, which is decomposed by heating. A thermal decomposition type thermoplastic radial block copolymer A having a reduced melt viscosity, an inelastic block having a glass transition point of 20 ° C. or higher and an elastic block, and a thermal crosslink having a melt viscosity increased by heating. And a thermoplastic radial block copolymer B of the present invention as a base polymer , the tackifier and the softening agent are
It is blended to prevent the adhesive component from seeping through the air holes of the adherend.
There is no such thing.

In the above-mentioned thermoplastic radial block block copolymers A and B, the non-elastic block is
Examples thereof include polymer blocks such as styrene-based polymers, acrylic polymers, vinyl chloride-based polymers, olefin-based polymers and urethane-based polymers, with polystyrene blocks being particularly preferred.

In the thermoplastic radial block copolymer A, a polyisoprene block is most suitable as the elastic block, but a partially hydrogenated polyisoprene block is also preferable. Further, in the thermoplastic radial block copolymer B, the polybutadiene block is the most suitable as the elastic block, but a partially hydrogenated polybutadiene block is also preferable. In this case, the greater the degree of hydrogenation of the polyisoprene block, the smaller the decrease in melt viscosity, and the greater the degree of hydrogenation of the polybutadiene block, the smaller the increase in melt viscosity.

In these thermoplastic radial block copolymers, for example, the thermoplastic radial block copolymer A'wherein the inelastic block is a polystyrene block (S) and the elastic block is a polyisoprene block (I).
Is generally expressed by _{(S-I) n Y (} n is 3 or more, Y represents a coupling bond). This thermoplastic radial block copolymer A ′ is a so-called thermal decomposition type, and has a property of being decomposed by heating and having its melt viscosity lowered.

Further, for example, a thermoplastic radial block copolymer B'wherein the inelastic block is a polystyrene block (S) and the elastic block is a polybutadiene block (I) is generally (SB) _n Y (n is 3 or more, Y represents a coupling bond). This thermoplastic radial block copolymer B'is a so-called heat-crosslinking type and has the property of increasing the melt viscosity by being crosslinked by heating.

The content of the inelastic block in any of the thermoplastic radial block copolymers A and B is generally 10 to 50% by weight, preferably 10 to 30% by weight in the copolymer A. %, And in copolymer B, it is 20 to 40% by weight. Further, in any of the thermoplastic radial block copolymers A ′ and B ′, the content of the polystyrene block, which is an inelastic block, is generally 10 to 50% by weight, preferably the copolymer A ′. Is 10 to 30% by weight, and that of the copolymer B'is 20 to 40% by weight.

When the content is less than 10% by weight, the elastic modulus and cohesive force of the above copolymer tend to be lowered, and therefore the adhesive force and heat resistance of the adhesive are lowered. On the contrary, if this content exceeds 50% by weight, the elastic modulus of the above-mentioned copolymer tends to be too high and the flexibility tends to be lost. Therefore, the adhesive force (tack) or the adhesive force and peeling of the adhesive are likely to occur. Strength etc. becomes low.

The blending ratio of the copolymer A and the copolymer B, or the blending ratio of the copolymer A'and the copolymer B ', is generally 2: 2 by weight (former: latter). 1-1: 4,
It is preferably 1: 1 to 1: 2.5.

The copolymers A and B or the copolymers A'and B'are preferably contained in an amount of 60% by weight or more based on the total amount of the base polymer, and 40% by weight. Other base polymers, for example, linear type thermoplastic block copolymers can be blended within a range not exceeding%.

As the linear type thermoplastic block copolymer, styrene-isoprene-styrene block copolymer (represented by SI-S), styrene-ethylene / propylene-styrene block copolymer (S- E / P
-S), styrene-butadiene-styrene block copolymer (represented by S-B-S), styrene-
Ethylene / butylene-styrene block copolymer (S-
E / B-S) is preferably used.

In the present invention, the above-mentioned base polymer is used, and a tackifier is added thereto. As the tackifier, coumarone-based resins, petroleum resins, terpene-based resins, rosin-based resins, phenol-based resins, xylene resins, and the like, which have good compatibility with various compounding agents, are used alone or in a mixture. As these tackifiers, those having a softening point of 70 to 160 ° C. are generally used, and
It is preferably blended in the range of 80% by weight.

A softening agent is also added. As the softening agent, olefin oligomers, paraffinic oils, naphthenic oils, vegetable oils, and the like, which have good compatibility with various compounding agents, may be used alone or as a mixture. Generally, these softening agents are preferably added in the range of 5 to 50% by weight.

Further, an antioxidant is usually added.
As the antioxidant, pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,3
5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythritol-tetrakis (β-lauryl-thiopropionate), tris (2,4-di-).
t-butylphenyl) phosphite, 2-t-butyl-
6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1
-(2-Hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate and the like are used alone or in combination. Generally, these heat stabilizers are preferably blended in the range of 0.1 to 3% by weight.

[0024] The above tackifier, a softening agent, can improve the performance of the adhesive by blending this <br/> like. In addition, additives such as an antioxidant, an ultraviolet absorber, a colorant, and an inorganic filler may be added if necessary.
The hot-melt adhesive of the present invention is prepared by mixing an appropriate amount of the above-mentioned various compounding agents, and using a roll, a Banbury mixer, a kneader, a kneading extruder, or the like, generally 100 to 20.
It is produced by melt-kneading at 0 ° C.

[0025]

The function of the hot melt adhesive of the present invention is 20 ° C.
The thermoplastic radial block copolymer consisting of an inelastic block having the above glass transition point and an elastic block,
Main chain is shorter than linear type thermoplastic block copolymer. Therefore, there is little entanglement with other molecules during heat melting, slippage between molecules is likely to occur, and a relatively low melt viscosity is obtained. Further, as compared with the linear type, a physical crosslink (domain structure) by the inelastic block phase and the elastic block phase is easily formed, and a relatively high cohesive force is obtained.

Further, using a radial block copolymer
Since a physical crosslink (domain structure) is formed so as to surround the tackifier and the softener, separation of low molecular weight components of these compounding agents is suppressed and exudation is eliminated.

Moreover, a thermal decomposition type thermoplastic radial block copolymer A which is decomposed by heating to reduce the melt viscosity
(For example, a copolymer A'wherein the non-elastic block is a polystyrene block and the elastic block is a polyisoprene block or a partially hydrogenated polyisoprene block),
Thermo-crosslinking type thermoplastic radial block copolymer B (for example, the non-elastic block is a polystyrene block and the elastic block is a polybutadiene block or a partially hydrogenated polybutadiene block) which is cross-linked by heating to increase the melt viscosity. When used in combination with B '), the high cohesive force and the adhesive force are further enhanced, and the melt viscosity is further reduced.

This is considered to be due to the following reason. That is, copolymer A (for example, copolymer A ′
) And the copolymer B (for example, the copolymer B ′) are mutually compatible and mixed together, and have a so-called bimodal molecular weight distribution, so that the copolymer A (A ′ at the time of thermal melting). )
Due to the thermal decomposition of the components, the melt viscosity as a whole is remarkably lowered, and the cohesive force is also lowered. However, this decrease in cohesion is
It is considered that the copolymer B (B ′) component is supplemented by thermal crosslinking, and a high cohesive force is developed as a whole after the adhesive is solidified. The copolymer A (A ') component also contributes to the improvement of tackiness.

[0029]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 As a pyrolytic thermoplastic radial block copolymer A in which the non-elastic block was a polystyrene block and the elastic block was a polyisoprene block, Quintac 3450 (trade name) manufactured by Zeon Corporation was used. This is represented by (S-I) ₃ Y.

As the thermo-crosslinking type thermoplastic radial block copolymer B in which the non-elastic block is a polystyrene block and the elastic block is a polybutadiene block, Sorprene T-414 (trade name) manufactured by Asahi Kasei Corporation was used. . This is represented by (S-B) ₄ Y.

Quintac 3450 (trade name) 1
1 part by weight, Sorprene T-414 (trade name) 15 parts by weight, hydrogenated alicyclic petroleum resin (Alcon M-105: Arakawa Chemical Co., Ltd.) 53 parts by weight as a tackifier, and paraffin as a softener. 21 parts by weight of oil (Shelex 371N: manufactured by Shell Chemical Company, USA) containing a system oil, 0.3 parts by weight of Sumitizer GM (trade name) of Sumitomo Chemical Co., Ltd. as an antioxidant, and Sumitomo Chemical Co., Ltd. Of SUMILIZER TP-D (trade name) of 0.3 part by weight, and kneading this with a universal mixing stirrer at 140 ° C.
A hot melt adhesive was produced.

Using this hot melt adhesive, the melt viscosity, cohesive force, thermal stability and exudation were measured by the following methods. The results are shown in Table 1.

(1) Melt viscosity The melt viscosity of the adhesive immediately after its production was measured at 140 ° C. using a BM type rotational viscometer.

(2) Cohesive strength The adhesive was heated and melted at 140 ° C., and this was applied to a polyethylene film in a bead shape at a coating amount of 0.08 g / m and immediately subjected to corona surface treatment (PE).
T) A test piece was prepared by pressure bonding to the film.

This test piece was subjected to a shear load of 100 g in the direction perpendicular to the length of the bead of 25 mm, put in a hot air circulation dryer at 40 ° C., and the time until the load dropped (holding time) was measured. did.

(3) 50 g of the heat-stable adhesive is put in a glass bottle, and 180
It was put in a hot air circulation dryer at ℃ for 72 hours, then taken out and immediately visually inspected for the presence of carbides and foreign matters.

100 g of the adhesive is put in a glass bottle,
Put it in a hot air circulation dryer at 150 ° C for 72 hours without a lid, then take it out and cool it immediately. Measure the melt viscosity of this adhesive at 140 ° C, and measure the melt viscosity measured in (1) above. The change in viscosity was investigated. In the table, + represents increase in viscosity and-indicates decrease in viscosity.

(4) The exuding adhesive was heated and melted at 140 ° C., and this was applied to a polyethylene film having a large number of fine air holes called a moisture permeable type in a bead shape at an application amount of 0.08 g / m, 6
The film was placed in a hot air circulation dryer at 0 ° C. for 48 hours, and the presence or absence of seepage of the adhesive on the film surface opposite to the coated surface was visually examined.

Example 2 In Example 1, Quintac 3450 (trade name) 6
Parts by weight were changed to 20 parts by weight of Sorprene T-414 (trade name). Other than that was performed like Example 1. The results are shown in Table 1.

Example 3 In Example 1, Quintac 3450 (trade name) 1
6 parts by weight and 10 parts by weight of Sorprene T-414 (trade name) were used. Other than that was performed like Example 1. The results are shown in Table 1.

Comparative Example 1 As a linear type thermoplastic block copolymer in which the non-elastic block is a polystyrene block and the elastic block is a poly (ethylene / butylene) block, Tuftec 1051 (trade name) and Tuftec manufactured by Asahi Kasei Corporation are used. 1
052 (trade name) was used. This is (SE / BS)
It is represented by.

10 parts by weight of Tuftec 1051 (product name) and 11 parts by weight of Tuftec 1052 (product name)
Hydrogenated alicyclic petroleum resin (Alcon P-
100: Arakawa Chemical Co., Ltd.) 60 parts by weight and paraffinic oil as a softening agent (Daphne Oil P)
W-90: manufactured by Idemitsu Petrochemical Co., Ltd.) 19 parts by weight, and Irganox 1010 manufactured by Ciba Geigy Co. as an antioxidant.
(Product name) 0.3 part by weight was blended, and this was kneaded with a universal mixing stirrer at 140 ° C. to produce a hot melt adhesive.

Using this hot melt adhesive, the melt viscosity, cohesive force, thermal stability and exudation were measured in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2 In Example 1, Quintac 3450 (trade name) 1
26 parts by weight of Sorprene T-414 (trade name) was used instead of 1 part by weight and 15 parts by weight of Sorprene T-414 (trade name). Other than that was performed like Example 1. The results are shown in Table 2.

Comparative Example 3 In Example 1, Quintac 3450 (trade name) 1
26 parts by weight of Quintac 3450 (product name) was used instead of 1 part by weight and 15 parts by weight of Sorprene T-414 (product name). In addition, Sumilizer GM as an antioxidant
(Product name) 0.3 parts by weight and Sumilizer TP-D (Product name) 0.3 parts by weight, Irganox 1010
(Product name) 0.3 part by weight was used. Otherwise, Example 1
I went the same way. The results are shown in Table 2.

Comparative Example 4 In Example 1, Quintac 3450 (trade name) 1
As a linear type thermoplastic block copolymer in which the non-elastic block is a polystyrene block and the elastic block is a polybutadiene block, 1 part by weight and 15 parts by weight of Sorprene T-414 (trade name) are manufactured by Asahi Kasei Corporation. Toughprene A (trade name) 26 parts by weight was used. This is represented by (S-B-S). Other than that was performed like Example 1. The results are shown in Table 2.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

As described above, the hot melt adhesive of the present invention comprises a non-elastic block having a glass transition point of 20 ° C. or higher and an elastic block, and is a thermal decomposition type which is decomposed by heating to lower the melt viscosity. A thermoplastic radial block copolymer A (for example, a copolymer A'wherein the inelastic block is a polystyrene block and the elastic block is a polyisoprene block or partially hydrogenated polyisoprene block);

A thermo-crosslinking type thermoplastic radial block copolymer B (for example, an inelastic block) comprising an inelastic block having a glass transition point of 20 ° C. or higher and an elastic block, which is crosslinked by heating to increase the melt viscosity. Is a polystyrene block and the elastic block is a polybutadiene block or a partially hydrogenated polybutadiene block B)),

Containing as a base polymer , tackifying
A softener and a softener are mixed to form an adhesive from the air holes of the adherend.
It does not bleed out, has high cohesive strength and adhesiveness, and has a low melt viscosity, good coating workability even when used at a relatively low temperature, and good thermal stability with little change in viscosity. A hot melt adhesive having properties is obtained.

The hot melt adhesive of the present invention is
In particular, it has good adhesiveness to a film or non-woven fabric made of polyrefin such as polyethylene or polypropylene, and is transparent and has good flexibility and durability.

Therefore, the hot-melt adhesive of the present invention has stable adhesive performance, and in particular, a polyolefin film or a nonwoven fabric having a large number of fine ventilation holes is used, and a stripe-shaped or dot-shaped adhesive is used. Diaper
Suitable for manufacturing sanitary napkins, bed pads, etc.

Claims (2)

(57) [Claims] 1. A pyrolytic thermoplastic radial block copolymer A which comprises an inelastic block having a glass transition point of 20 ° C. or higher and an elastic block and decomposes by heating to reduce the melt viscosity, and 20 ° C. It contains a non-elastic block having the above glass transition point and an elastic block, and contains a thermo-crosslinking type thermoplastic radial block copolymer B which is cross-linked by heating to increase the melt viscosity as a base polymer and imparts tackiness. Aeration agent and softening agent are mixed to ventilate the adherend
A hot melt adhesive that does not exude the adhesive component from the holes . 2. A thermoplastic radial block copolymer A ′ in which the inelastic block is a polystyrene block and the elastic block is a polyisoprene block or a partially hydrogenated polyisoprene block, and the inelastic block is a polystyrene block, and The hot melt adhesive according to claim 1, which comprises a thermoplastic radial block copolymer B'wherein the block is a polybutadiene block or a partially hydrogenated polybutadiene block.