JP5063720B2 - Novel adhesive composition - Google Patents

Description

  The present invention relates to a low-viscosity adhesive composition, which is based on a block copolymer composition having a specific structure and has an excellent balance of holding power, tack and melt viscosity, and further has a low viscosity.

  In recent years, hot melt adhesives have been widely used from the viewpoints of environmental pollution and working environment. As a base polymer of a hot melt adhesive, a monoalkenyl aromatic compound-conjugated diene block copolymer (SBS, SIS, etc.) is widely used. However, for example, SBS has an insufficient balance between holding force and tack performance and melt viscosity, and improvements in these performances have been desired. As an improvement method thereof, JP-A-64-81877, JP-A-61-278578 and “Adhesion” (No. 32-1, page 27, '88) describe triblock copolymers and diblock copolymers. An adhesive composition comprising a coalescence is disclosed. Further, JP-A-61-261310 and JP-A-63-248817 disclose a block copolymer obtained by coupling with a specific bifunctional coupling agent (aliphatic monoester, specific dihalogen compound). An adhesive composition comprising a polymer is disclosed.

  However, recently, the required performance for hot melt adhesives has been further advanced. For example, adhesives used for sanitary materials such as disposable diapers and napkins using SBS are from the viewpoint of hygiene and workability. There is a need for an adhesive that is very clear (clear and colorless) and has a lower viscosity. However, SBS generally has poor thermal stability because it has a vinyl bond in the conjugated diene polymer block, and is likely to be discolored during processing at high temperatures, or to be deteriorated in performance due to gelation, thermal decomposition, or the like. On the other hand, when processed at a low temperature, discoloration and performance deterioration can be suppressed, but the melt viscosity of the adhesive composition becomes high and processing becomes difficult. Also, if the amount of SBS added is low, processing at low temperatures is facilitated and a clear and low viscosity adhesive is obtained, but it is virtually impossible to maintain the desired adhesive performance.

  In addition, when the molecular weight of SBS is lowered, processing at low temperature becomes easy, discoloration and performance deterioration can be suppressed, and an adhesive having a low viscosity can be obtained, but still satisfactory adhesive performance cannot be obtained. There was a problem. In light of this technical background, the object of the present invention is clear processing that is easy to process at low temperatures, has excellent adhesive properties such as holding power and tack performance, has a low melt viscosity and is colorless and excellent in transparency. It is providing the adhesive composition which is easy.

  As a result of intensive studies to develop the above-mentioned preferable adhesive composition, the present inventors have obtained a monoalkenyl aromatic compound-conjugated diene block copolymer composition having a certain specific structure. The present invention has been completed based on this finding based on the finding that an adhesive composition comprising a specific additive and a specific additive is suitable for the purpose.

  According to the present invention, a clear adhesive composition that is easy to process at low temperatures, has excellent adhesive properties such as holding power and tack performance, and has a low melt viscosity and is colorless and excellent in transparency can be obtained. .

That is, the present invention provides: (A) a block copolymer combination (a) comprising a polymer block mainly composed of at least two monoalkenyl aromatic compounds and a polymer block mainly composed of at least one conjugated diene; A block copolymer composition comprising a block copolymer (b) comprising a polymer block mainly composed of at least one monoalkenyl aromatic compound and a polymer block mainly composed of at least one conjugated diene. , (A) is greater than 27% by weight and 50% by weight or less , (b) is 50% by weight or more and less than 73% by weight , and (a) has a peak molecular weight of 70,000 to 11. 90,000, the peak molecular weight of (b) is 20,000 to 58,000 in terms of standard polystyrene, and the content of all monoalkenyl aromatic compounds is 21 to 40% by weight, and 5% toluene solution viscosity of 10～40Cps, block copolymer (a), the block copolymer (b), obtained by coupling reaction using at least one alkoxysilicon Motokei coupling agent Cup A block copolymer composition that is a ring polymer, and (B) a tackifying resin, and (A) 100 parts by weight of (B) 20 to 400 parts by weight is contained. It is an adhesive composition.

  The present invention is described in detail below. The component (A) constituting the present invention is a block co-merging (a) comprising a polymer block mainly composed of at least two monoalkenyl aromatic compounds and a polymer block mainly composed of at least one conjugated diene. And a block copolymer (b) comprising a polymer block mainly composed of at least one monoalkenyl aromatic compound and a polymer block mainly composed of at least one conjugated diene. It is.

  The polymer block mainly composed of a monoalkenyl aromatic compound is a monoalkenyl aromatic compound containing 50 to 100% by weight of a monoalkenyl aromatic compound alone or a copolymer block with a conjugated diene. The polymer block mainly composed of conjugated diene is a conjugated diene compound alone containing 50 to 100% by weight of conjugated diene or a copolymer block with a monoalkenyl aromatic compound. The monoalkenyl aromatic compound in the copolymer block mainly composed of conjugated diene may be uniformly distributed or non-uniformly (for example, tapered). Further, the block copolymers (a) and (b) may be obtained by simultaneously or separately hydrogenating conjugated dienes or monoalkenyl aromatic compounds, and these block copolymers are further modified with a modifier such as maleic anhydride. It may also be a linear block copolymer modified with.

  Examples of the monoalkenyl aromatic compound used in (a) and (b) include monomers such as styrene, p-methylstyrene, tertiary butylstyrene, α-methylstyrene, and 1,1-diphenylethylene. Among them, styrene is preferable. These monomers may be used alone or in combination of two or more. On the other hand, examples of the conjugated diene used in (a) and (b) include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3- Monomers such as octadiene, phenyl-1,3-butadiene and the like can be mentioned, among which 1,3-butadiene and isoprene are preferable. These monomers may be used alone or in combination of two or more.

  The block copolymer (a) and the block copolymer (b) are present in a ratio of 5 to 50% by weight of the block copolymer (a) and 50 to 95% by weight of the block copolymer (b). It is essential to do. When there are more block copolymers (a) than this, solubility will worsen and the melt viscosity of an adhesive composition will also become high. Moreover, when it is less than this, the high balance of tack, adhesive force, and holding power is not expressed. The range of a preferable block copolymer (b) is 52 to 88% by weight, and more preferably 55 to 85% by weight.

The molecular weight of the block copolymer (a) is essential to be 60,000 to 120,000 in terms of standard polystyrene as measured by gel permeation chromatography (GPC). When larger than this, since the melt viscosity of an adhesive composition is too high, it is unpreferable from points, such as an energy loss at the time of melt | dissolving, and the capability of a stirrer. Moreover, when smaller than this, various adhesive performances, such as a tack, adhesive force, and retention strength, are inferior, and it is not preferable. The preferred molecular weight range is 70,000-
It is 115,000, More preferably, it is 80,000-110,000. The molecular weight of the block copolymer (b) is essential to be 10,000 to 60,000 in terms of standard polystyrene as measured by GPC. Even if it is larger or smaller than this, a high balance of tack, adhesive strength, holding power and melt viscosity is not expressed. The range of a preferable molecular weight is 20,000 to 58,000, and more preferably 40,000 to 55,000.

  The content of the monoalkenyl aromatic compound (a) and (b) is 21% by weight or more and 40% by weight or less, respectively. When the content of the monoalkenyl aromatic compound is less than 21%, the cohesive strength of the monoalkenyl aromatic compound decreases and sufficient holding power is not expressed. When the content exceeds 50%, the tack and adhesive strength are poor. It is not preferable. A preferable range is 25 to 39% by weight, more preferably 30 to 38% by weight of the monoalkenyl aromatic compound.

The viscosity of the 15% toluene solution of the block copolymer composition of the present invention is 10 to 40 cps measured at 25 ° C. If it is less than 10 cps, a high balance of tack, adhesive strength and holding power is not expressed. On the other hand, if it exceeds 40 cps, the melt viscosity of the adhesive composition becomes too high when processed at a relatively low temperature, which makes it very difficult to produce. A preferred range is 12 to 38 cps, more preferably 15 to 35 cps.

  The block copolymer composition (A) comprising the block copolymer (a) and (b) constituting the present invention is polymerized with styrene using, for example, an organolithium compound as a polymerization initiator in an inert hydrocarbon solvent. Then, butadiene is polymerized, and further, these operations are repeated, and the two types of block copolymers (a) and (b) obtained by repeating these operations are mixed. After the completion of the polymerization reaction, the mixing method is such that water, alcohol, acid, etc. are added to blend the polymerization solution of each component in which the active species are deactivated, and then, for example, steam stripping or the like is performed to form a polymerization solvent. Is obtained by separating and then drying. Moreover, the polymer obtained by separating and drying the polymerization solvent individually can be obtained by blending with a roll or the like.

  The block copolymer composition (A) comprising the block copolymer (a) and (b) constituting the present invention can also be obtained by another method. That is, the copolymer obtained by polymerizing the block copolymer (b) by the same method as described above and then adding a predetermined amount of a suitable polyfunctional coupling agent to the organolithium compound in the polymerization system. The combined product is (a), and the desired composition is obtained in the same reaction system. When this method is used, the molecular weight and molecular weight distribution of the polymer block part mainly composed of monoalkenyl aromatic compounds are the same in (a) and (b), so that the cohesive force of the block copolymer composition is improved. And very good adhesion performance. Further, the polymerization operation is simple and this method is desirable.

  Examples of the coupling agent include bifunctional epoxy compounds, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethoxymethylsilane, tetramethoxysilane, and alkoxysilicon compounds such as tetraethoxysilane, dichlorodimethylsilane, and phenylmethyl. Halogenated silicon compounds such as dichlorosilane, trimethoxymethylsilane, tetramethoxysilane, tetraethoxysilane, tin compounds such as dichlorodimethyltin and tetrachlorotin, ester compounds such as methylbenzoate, divinylbenzene, etc. And vinyl allenes. Among these, bifunctional coupling agents are preferably used from the viewpoint of adhesive performance. Also. From the viewpoint of coloring when the adhesive composition is heated, a non-halogen coupling agent preferably containing no halogen is preferably used. Specifically, it is an alkoxy silicon compound such as a bifunctional epoxy compound or dimethyldimethoxysilane.

The component (B) constituting the present invention is not particularly limited, and is a rosin terpene resin, a hydrogenated rosin terpene resin, a coumarone resin, a phenol resin, a terpene-phenol resin, an aromatic hydrocarbon resin, Known tackifying resins such as aliphatic hydrocarbon resins can be used, and these tackifying resins can be used alone or in admixture of two or more. The amount used is 20 to 400 parts by weight, preferably 50 to 350 parts by weight, based on 100 parts by weight of the block copolymer composition (A). If the amount used is less than 20 parts by weight, the tackiness of the adhesive composition is difficult to be imparted, and if it exceeds 400 parts by weight, the holding power of the adhesive composition is reduced. Impairs adhesive properties.

  The adhesive composition of the present invention can use known naphthenic and paraffinic process oils and mixed oils as softeners. By adding the softening agent, the viscosity of the adhesive composition is reduced, so that the workability is improved and the tackiness is improved. Aroma-based oils are not preferred because they impair the color tone and thermal stability of the adhesive composition. The amount used is in the range of 10 to 200 parts by weight per 100 parts by weight of the block copolymer composition (A). The effect is not exhibited at 10 parts by weight or less, and when it exceeds 200 parts by weight, the holding power of the adhesive composition is significantly impaired. Preferably it is 20-150 weight part, More preferably, it is 30-100 weight part.

  The adhesive composition of the present invention is particularly preferable because the discoloration during heating is suppressed by adding an antioxidant. Examples of the antioxidant include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,4-bis [(octylthio) methyl] -0- Cresol, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl-6- [1- ( 3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl)] acrylate Sulfur antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate pentaerythritol-tetrakis (β-lauryl thiopropionate); tris (nonylphenyl) phosphite, tris ( And phosphorus-based antioxidants such as 2,4-di-t-butylphenyl) phosphite. The added amount thereof is in the range of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the adhesive composition. If the amount is too small, the thermal stability is inferior. If the amount is too large, the color changes upon heating. A desirable range is 0.1 to 4 parts by weight, and more preferably 0.5 to 3 parts by weight.

  Further, in some cases, it is possible to use a light stabilizer in addition to the antioxidant. Examples of such a light stabilizer include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 2- (2′-hydroxy-3 ′, 5′-t-butylphenyl) benzotriazole. , 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzazotriazole and other benzotriazole ultraviolet absorbers, 2-hydroxy-4-methoxybenzophenone, etc. Benzophenone ultraviolet absorbers or hindered amine light stabilizers.

In addition to the above-described stabilizer, the adhesive composition of the present invention may optionally include pigments such as bengara and titanium dioxide; waxes such as paraffin wax, microcrystalline wax, and low molecular weight polyethylene wax; amorphous polyolefin, Polyolefin or low molecular weight vinyl aromatic thermoplastic resins such as ethylene-ethyl acrylate copolymer; natural rubber; polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, acrylic rubber, isoprene Synthetic rubber such as isobutylene rubber, polypentenamer rubber, and styrene-isoprene block copolymer other than the present invention may be added. The adhesive composition of the present invention is prepared by a uniform mixing method under heating with a known mixer, kneader or the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these Examples do not limit this invention. Various measurements were performed according to the following methods.
1. Analysis method
A. Physical properties of polymer 1 and linear block copolymer composition
(1) Total styrene amount Calculated from the absorption intensity at 262 nm using an ultraviolet spectrophotometer (Hitachi UV200).
(2) Amount of block styrene The amount of block styrene was determined according to the oxidative decomposition method using osmium tetroxide and t-butyl hydroperoxide (described in “Journal of Polymer Science”, Vol. 1, page 429 (1946)). The weight of the styrene polymer block was calculated from the absorption intensity at 262 nm using an ultraviolet spectrophotometer (Hitachi UV200).
(3) Microstructure The microstructure was measured using an infrared spectrophotometer (model 1710 manufactured by Perkin Elmer) and measured by the Hampton method (described in “Analytical Chem., 21, 943 ('43)”).

(4) GPC
GPC [The apparatus is manufactured by Waters, and the column is a combination of two ZORBAXPSMlOOOO-S manufactured by DuPont and a total of three PSM 60-S. Tetrahydrofuran was used as the solvent, and the measurement conditions were a peak molecular weight and a composition ratio from a chromatogram of a temperature of 35 ° C., a flow rate of 0.7 ml / min, a sample concentration of 0.1% by weight, and an injection volume of 50 μl. The peak molecular weight is a conversion value from the following standard polystyrene (Waters) calibration curve. 1.75 x 10 ⁶ , 4.1 x 10 ⁵ , 1.12 x 10 ⁵ , 3.5 x 10 ⁴ , 8.5 x 10 ³
(5) 15% toluene solution viscosity of 15% toluene solution viscosity, Cannon - Fenske with viscosity tube was measured in a constant temperature bath which is managed at a temperature of 25 ° C..

B. Measurement of physical properties of adhesive The physical properties of the adhesive composition were measured by taking out the composition in a molten state, coating the polyester film with an applicator to a thickness of 50 μm, and preparing an adhesive tape sample. Tack, adhesive strength, and retention strength were measured by the following methods.
(1) Loop tack A loop-shaped sample having a length of 250 mm and a width of 15 mm was used, and measurement was performed at a contact area: 15 mm × 50 mm, an adhesion time: 3 sec, and an adhesion and peeling speed: 500 mm / min.
(2) Holding force Holding force is applied in accordance with JIS Z-1524 so that an area of 25mm x 25mm is in contact with the stainless steel plate, and a load of 1kg is applied at 60 ° C until the adhesive tape slips off. Was measured.
(3) Melt viscosity The melt viscosity of the adhesive composition was measured at 180 ° C. using a Brookfield viscometer.

(4) Adhesive strength A sample having a width of 25 mm was attached to a polyethylene plate, and the 180 ° C. peeling force was measured at a peeling speed of 300 mm / min.
(5) Softening point The softening point was measured by the ring and ball method according to JIS K-2207.
(6) Heat discoloration The thermal stability of the adhesive was evaluated by a four-step evaluation of ◯, Δ, ×, and XX by examining the color tone after heating in a gear oven at 190 ° C. for 24 hours. (○ is the best, XX is the worst.)

Example 1
A 10 liter stainless steel reactor equipped with a jacket and a stirrer was sufficiently purged with nitrogen, then charged with 7060 cc of cyclohexane, 1.41 g of tetrahydrofuran, and 350 g of styrene, and warm water was passed through the jacket to set the content at about 70 ° C. Thereafter, an n-butyllithium cyclohexane solution (pure 1.80 g) was added to initiate styrene polymerization. After the styrene was completely polymerized, 650 g of butadiene (1,3-butadiene) was added to continue the polymerization. After the butadiene was almost completely polymerized, a very small amount of the polymerization solution was sampled as the component (b). . Immediately thereafter, 0.69 g of the coupling agent described in Table 1 was added and coupled. After adding the coupling agent, 0.5 g of water was added. Immediately after the styrene was charged, the system was continuously stirred with a stirrer during this period.

  Thereafter, the solution of the block copolymer composition was taken out, 1.9 g of 2,6-di-tert-butyl-4-methylphenol and 1.2 g of tris (nonylphenyl) phosphite were added, and the resulting solution was obtained. The solvent was removed by steam stripping, followed by dehydration and drying with a hot roll (120 ° C.) to obtain a block copolymer. These operating conditions are summarized in Table 1. The block copolymer composition thus obtained has a styrene content of 35% by weight, the peak molecular weight of the block copolymer measured by GPC is 113,000 on the high molecular side, and the peak on the low molecular side. The molecular weight was 55,000. Further, the ratio of the coupled components in the entire block copolymer was 25% by weight. The 15% toluene solution viscosity was 25 cps. The sampled component (b) had a styrene content of 35% by weight. These measured values are summarized in Table 2.

150 g of the obtained block copolymer is 100 parts by weight of the block copolymer, 250 parts by weight of Alcon M100 (manufactured by Arakawa Chemical Co., Ltd .: trade name) as a tackifying resin, and Diana Process Oil PW as a softening agent. -90 (made by Idemitsu Kosan Co., Ltd .: trade name), 60 parts by weight, and Sumilizer GM (made by Sumitomo Chemical Co., Ltd .: trade name) as a heat stabilizer at a blending ratio of 1 part by weight. The mixture was melt-kneaded in a liter container equipped with a stirrer to obtain a hot-melt adhesive composition. The viscosity of the adhesive composition was 3720 cps at 140 ° C., 1620 cps at 160 ° C., and 860 cps at 180 ° C. The softening point was measured and found to be 84 ° C. Furthermore, the probe tack was 2000 gf, the adhesive strength was 1450 gf / 10 mm, and the holding force was 3 minutes. These measured values are summarized in Table 3.

(Examples 2-6, Comparative Examples 1-2)
Polymerization was performed under the same conditions as in Example 1 except for the conditions shown in Table 1, and each block copolymer was obtained by the same operation. The analysis result of the obtained block copolymer is shown in Table-2. Further, a hot melt adhesive composition was obtained in the same manner as in Example 1. The physical property measurement results of the adhesive composition are shown in Table 3.
From the Examples and Comparative Examples, it can be seen that the adhesive composition of the present invention has a low viscosity and exhibits excellent adhesive performance.

Claims (4)

(A) a block copolymer (a) comprising a polymer block mainly composed of at least two monoalkenyl aromatic compounds and a polymer block mainly composed of at least one conjugated diene, and at least one monoalkenyl A block copolymer composition comprising a block copolymer (b) comprising a polymer block mainly comprising an aromatic compound and a polymer block mainly comprising at least one conjugated diene, the proportion of (a) Is greater than 27% by weight and 50% by weight or less , the proportion of (b) is 50% by weight or more and less than 73% by weight , and the peak molecular weight of (a) is 70,000 to 119,000 in terms of standard polystyrene, (b) Has a peak molecular weight of 20,000 to 58,000 in terms of standard polystyrene, and a total monoalkenyl aromatic compound content of 21 to 40% by weight, and a 15% toluene solution viscosity. Block There is 10～40Cps, block copolymer (a), the block copolymer (b), a coupling polymer obtained by coupling reaction using at least one alkoxysilicon Motokei coupling agent A pressure-sensitive adhesive composition comprising a copolymer composition and (B) a tackifying resin, and comprising (B) 20 to 400 parts by weight with respect to 100 parts by weight of (A). . The composition according to claim 1, wherein the alkoxysilicon coupling agent is a bifunctional coupling agent. A softening agent, viscosity to the adhesive composition 100 parts by weight, the composition according to claim 1 or 2, characterized in that it contains 10 to 200 parts by weight. The composition according to any one of claims 1 to 3 , wherein the antioxidant is contained in an amount of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the adhesive composition.