JP2539813B2 - Adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a polyurethane-based adhesive composition.

[Prior Art] As a one-pack type reactive adhesive, an adhesive containing a polyurethane prepolymer having an isocyanate group is known. The isocyanate group can react with moisture in the air or the material to be adhered, whereby the polyurethane prepolymer is reactively cured and exerts an adhesive force. This adhesive can be dissolved in a solvent and used, but it is usually used without a solvent. The adhesive applied to the adherend by coating or the like gradually reacts and cures due to the moisture in the air. However, the reaction curing time is not so short. With liquid adhesives, therefore, the initial adhesive strength is often insufficient. On the other hand, a hot-melt type adhesive is known as a one-component reactive adhesive having improved initial adhesive strength. This is an adhesive containing a polyurethane prepolymer that is solid at room temperature, and is heated and melted and applied to the adherend. The initial adhesive force of this adhesive is exerted by the cohesive force due to the adhesive solidifying by cooling after application. On the other hand, the reaction of the isocyanate group gradually progresses separately from that, and the final adhesive force is achieved by the reactive curing with the isocyanate group as described above. In order to further enhance the initial adhesive strength of the hot melt type adhesive, it is known to add a tackifier, and it is described in, for example, JP-A-61-115977. Known tackifiers include, for example, coumarone resin, terpene-phenol resin, rosins, and styrene resins.

[Problems to be Solved by the Invention] For example, when a porous material such as woven cloth, non-woven cloth, artificial leather, or a film or sheet of porous plastic is used as an adherend, and those materials or other materials are brought into contact with each other. In terms of workability at the time of application such as coating, a low viscosity at the time of applying the adhesive is required. In addition, in order to improve productivity, it is required that the adhesive force is exerted to a certain degree or more immediately after the adhesive is applied, and the adhesive having the high initial adhesive force is preferable. In particular, it is preferable that the viscosity of the material to be adhered rapidly increases as it is cooled after being applied. However, although the hot-melt type adhesive has a high initial adhesive strength, it has a high viscosity during melting and is not sufficient in terms of workability and permeability. Further, the rate of increase in viscosity with cooling is not so high that unless it is sufficiently cooled, high initial adhesive strength is not exhibited.

On the other hand, adhesives for clothing are required not to lose their adhesive strength during water washing or solvent washing (water resistance, solvent resistance), and be a soft adhesive. In many cases, ordinary polyurethane-based adhesives using polyester-based polyols have insufficient water resistance, and polyurethane-based adhesives using polyoxypropylene-based polyols have insufficient solvent resistance and flexibility. Therefore, in the case of adhering a porous material for clothing, in addition to the above, an adhesive that satisfies these required physical properties is required.

[Means for Solving Problems] The present inventors have studied and investigated solutions to the above problems in order to find a one-component reactive adhesive excellent in application to porous materials such as clothing materials. As a result, a new polyurethane-based adhesive composition was found. The present invention relates to the following adhesive composition.

The viscosity at 25 ° C. obtained by adding and reacting 1.2 to 2.4 times equivalent amount of diisocyanate compound to polyols mainly composed of polyoxytetomethylene diol is 10,000 to
80,000 centipoise polyurethane prepolymer 50-90
Polystyrene oligomer with a weight percentage of less than 2000
Including 10 to 50% by weight, the viscosity at 100 ℃ is 500 to 6000
A polyurethane-based adhesive composition that is centipoise.

The polyoxytetramethylene-based diol in the present invention is a diol having an oxytetramethylene group as a main component as a polymerized unit. This polyoxytetramethylene diol is a polymer having substantially only an oxytetramethylene group as a polymerized unit obtained by adding only tetrahydrofuran to a bifunctional initiator (hereinafter referred to as PTMG), as well as an oxytetramethylene group. It may be a copolymer having Examples of the copolymer include a polymer obtained by mixing a bifunctional initiator with tetrahydrofuran and a copolymerizable cyclic ether such as alkylene oxide or sequentially adding them, and an addition polymerizable cyclic ether such as alkylene oxide to PTMG. Polymers obtained by addition of addition copolymerizable cyclic ester such as or caprolactone, polymers obtained by addition of tetrahydrofuran to a bifunctional polymeric diol, and polyesters of PTMG and dicarboxylic acids. The proportion of oxytetramethylene groups in all polymerized units in these copolymer-based polyoxytetramethylene-based diols exceeds at least 50% by weight, preferably
It is 75% by weight or more. A dihydric alcohol is suitable as the bifunctional initiator, and propylene oxide and ethylene oxide are preferred as the cyclic ether.
Furthermore, the molecular weight of this polyoxytetramethylene diol is preferably about 600 to 3000, and more preferably about 800 to 2500. If the molecular weight is too low, the flexibility of the resulting adhesive decreases, while if it is too high, the viscosity increases.

The polyols in the present invention contain the above-mentioned polyoxytetramethylene diol as a main component (that is, it exceeds 50% by weight). The polyoxytetramethylene-based diols may be used in combination of two or more thereof, and may be used in combination with other polymeric polyols. Other polymeric polyols include, for example, polyether polyols such as polyester polyols and polyoxypropylene polyols. The ratio of the polyoxytetramethylene-based diol to the total of the polyoxytetramethylene-based diol and the other polymeric polyol is preferably about 80-100% by weight. The ratio of oxytetramethylene groups to all polymerized units in the total of these polymeric polyols is preferably about 70 to 100% by weight. The molecular weight of the other polymeric polyol is not particularly limited, and the molecular weight per hydroxyl group thereof is preferably in the range of about the same as the molecular weight per hydroxyl group of the polyoxytetramethylene diol. That is, about 300 to 1500, especially about 400 to 13 per hydroxyl group.
00 is appropriate. The number of hydroxyl groups is suitably 2 to 4, and a diol having 2 is particularly preferable. When a relatively large number of polyols having a high number of hydroxyl groups is used, the flexibility of the adhesive tends to decrease.

As polyols, lower molecular weight polyols,
For example, a polyhydric alcohol such as a dihydric alcohol or a trihydric alcohol, or a polymeric polyol having a lower molecular weight than the polymeric polyol may be used in combination. Specific examples thereof include erylene glycol, 1,4-butanediol, triethanolamine and the like. The combined use of these low-molecular-weight polyols has the effect of increasing the mechanical strength of the adhesive, but decreases the flexibility, and it is not preferable to use a relatively large amount. Although a small amount of polyamine or the like can be used together with the polyols, it is not appropriate to use a relatively large amount for the same reason.

It is preferable that the polyols as the main component of the polyoxytetramethylene-based diol in the present invention consist essentially of at least one polyoxytetramethylene-based diol. Further, as the polyoxytetramethylene-based diol, a copolymer containing PTMG or an oxytetramethylene group having a high proportion of oxytetramethylene groups and another oxytetramethylene is preferable.

1.2 to 2.4 times the equivalent of the above polyols (the ratio of isocyanate group to one hydroxyl group is 1.2 to 2.4)
A polyurethane prepolymer is obtained by adding and reacting 2.4) diisocyanate compounds.
The excess polyisocyanate compound may remain unreacted. More preferable amount of the diisocyanate compound is
It is 1.3 to 2.1 times equivalent to the polyols. The reaction of the diisocyanate compound is usually performed under heating. If necessary, the reaction can be performed in the presence of a catalyst such as an organotin compound.

As the diisocyanate compound, aromatic, aliphatic,
Diisocyanate compounds such as alicyclic compounds can be used. For example, diphenyl diisocyanate, tolylene diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, α,
Examples include α, α ′, α′-tetramethylxylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorodiisocyanate, and methylenebis (cyclohexyl isocyanate). 4.4'-Diphenylmethane diisocyanate is preferred from the viewpoint of reactivity and low toxicity. When yellowing is not required, yellowing-free diisocyanates such as xylylene diisocyanate and isophorone diisocyanate are used.

The viscosity of the polyurethane prepolymer at 25 ° C. is required to be 10,000 to 80,000 centipoise (hereinafter referred to as cp). If the viscosity is higher than this, the viscosity at the melting temperature of the adhesive composition described below becomes too high, and the workability is lowered. On the other hand, if it is too low, the permeability of the adhesive to the porous material becomes too high and the initial adhesive strength becomes insufficient. More preferable viscosity at 25 ° C is 30,000 to 60,000 cp
Is. The isocyanate group content of the polyurethane prepolymer is preferably 1 to 8% by weight, and particularly 3
~ 6 wt% is preferred.

The adhesive composition in the present invention contains a tackifier in order to secure the initial adhesive strength. The tackifier must be capable of exhibiting a sufficiently high adhesive strength at low temperatures, but in addition it must have low viscosity at the melting temperature and high compatibility with the polyurethane prepolymer. . Therefore, as the tackifier, a polystyrene-based oligomer having a relatively low molecular weight is used. The polystyrene-based oligomer (“Picotex 100”: molecular weight 3000, melting point 100 ° C.) described in the above-mentioned known examples is insufficient in this respect, and it is necessary to use a polystyrene-based oligomer having a lower molecular weight. Further, other tackifiers have insufficient compatibility. The molecular weight of the polystyrene-based oligomer, which is the tackifier in the present invention, is 2000 or less, preferably 300 to 1500. Polystyrene oligomers include styrene and α
A homopolymer such as methylstyrene or a copolymer with other monomers having it as the main monomer.

It is necessary that the content of the polyurethane prepolymer in the adhesive composition of the present invention is 50 to 90% by weight, and the content of the polystyrene oligomer is about 10 to 50% by weight. Particularly preferably, a polyurethane prepolymer
60-80% by weight and polystyrene oligomer 20-40% by weight
including. When the amount of the polystyrene-based oligomer is too large, a portion which does not dissolve in the polyurethane-based prepolymer is likely to be formed and the melt viscosity is increased. Furthermore, it tends to cause a decrease in the adhesive strength after curing. On the other hand, if the amount is too small, the initial adhesive strength will be insufficient. The adhesive composition in the present invention may consist of only these two components, but may contain a small amount of other components. However, when other components are blended, it is necessary to blend a small amount of one that does not hinder the performance of the composition of the present invention. Other components include, for example, antioxidants, light stabilizers, stabilizers such as ultraviolet absorbers, colorants, flame retardants and the like.

The adhesive composition of the present invention needs to have a viscosity at 100 ° C. of 500 to 6000 cp. More preferably 500-3000 cp, most preferably 800-25
It is 00cp. If the viscosity is higher than this, the workability is poor, and if it is lower than this, the initial adhesive strength is insufficient and the permeability is too high. The melting temperature (working temperature) of the adhesive composition of the present invention is preferably 60 to 120 ° C, particularly 80 to 110 ° C, but is not limited thereto.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Examples Synthesis Example 1 4.4 parts of 100 parts of PTMG having a molecular weight of 1000 (parts by weight, the same applies hereinafter)
-45 parts of diphenylmethane diisocyanate (hereinafter referred to as MDI) (NCO / OH = 1.8) was added, and the mixture was reacted at 80 ° C. for 4 hours. The obtained polyurethane prepolymer had an isocyanate group content of 4.6% by weight and a viscosity at 25 ° C of 50,000c.
It was p. Hereinafter, this prepolymer is referred to as Prepolymer A
Say.

Synthesis Example 2 30 parts of xylylene diisocyanate (NCO / OH = 1.6) was added to 100 parts of PTMG having a molecular weight of 1000 and reacted at 90 ° C. for 5 hours. The isocyanate group content of the obtained polyurethane prepolymer was 3.8% by weight, and the viscosity at 25 ° C was 40,000 cp.
Met. Hereinafter, this prepolymer is referred to as prepolymer B.

Synthesis example 3 MDI 100 parts (NCO / OH = 2.0) to PTMG 200 parts with a molecular weight of 2000
Was added and reacted at 80 ° C. for 4 hours. A polyurethane prepolymer (referred to as prepolymer C) having an isocyanate group content of 2.8% by weight and a viscosity at 25 ° C. of 60,000 cp was obtained.

Synthesis Example 4 MDI 45 parts (NCO / OH = 1.8) was added to 100 parts of a diol having a molecular weight of 1000 obtained by adding a mixture of propylene oxide / ethylene oxide = 40/60 (wt ratio) to PTMG having a molecular weight of 650, and 90 ° C. After reacting for 4 hours, the isocyanate group content is 4.6.
A polyurethane prepolymer having a weight percentage of 40,000 cp at 25 ° C. (referred to as prepolymer D) was obtained.

Example A polystyrene-based tackifier (melting point: 75 ° C.) having a molecular weight of about 400, which was preheated and melted in a prepolymer A heated at 100 ° C.
Was added and mixed to produce an adhesive composition having the tackifier content of 35% by weight.

Similarly, prepolymers B to D and a polystyrene-based tackifier having a molecular weight of about 400 were mixed to produce an adhesive composition shown in Table 1 below. The viscosities of these compositions at 25 ° C, 50 ° C and 100 ° C are shown in Table 1.

The following evaluation tests were performed using these adhesive compositions.
The results are shown in Table 1.

Evaluation Test The adhesive composition was kept at 100 ° C., and a polyethylene terephthalate film was applied to a thickness of 50 μm using an applicator heated to 100 ° C., and a nylon cloth was immediately laminated thereon. Next, the adhesive was placed in a thermo-hygrostat to cure the adhesive composition. Observation of the final bonded product revealed that the nylon fabric hardly penetrated the adhesive and was cured to such an extent that a large force was required to separate the film and the fabric.

Table 1 shows the results of a four-level evaluation of the adhesiveness of the adhesive before being placed in the constant temperature and humidity chamber and the adhesiveness of the final adhesive (➝>∘>Δ> × in order of increasing adhesive strength). The workability is good when the viscosity at 100 ° C is 2000 cp or less, and good when it is 1500 cp or less.

Comparative Example 1 Only prepolymer A was used as an adhesive. Table 1 shows the results of the same evaluations as in the examples.

Comparative Example 2 An adhesive composition was produced in the same manner as in the example from 400 parts of prepolymer A and 600 parts of the same polystyrene-based tackifier as in the example. The evaluation is shown in Table 1.

Comparative Example 3 An adhesive composition was produced in the same manner as in the example using 650 parts of prepolymer A and 350 parts of an alkylphenol resin tackifier. The evaluation is shown in Table 1.

[Advantages of the Invention] The adhesive composition of the present invention has a lower viscosity at working temperature than that of a conventional hot melt type one-pack type reactive adhesive and has good workability. Moreover, the viscosity when cooled to room temperature is high and the initial adhesive strength is good. Further, as shown in the above-mentioned Examples, the viscosity at 50 ° C. is high. This means that its viscosity increases rapidly with cooling. Therefore, in the case of continuously adhering long products, the temperature at which the adhesive force starts to be exerted is high and the adhering work can be performed at high speed. On the other hand, since the main component is a polyurethane prepolymer using a polyoxytetramethylene diol, the adhesive has high water resistance and solvent resistance.

These characteristics make the adhesive composition of the present invention suitable for adhering porous materials, preferably fibrous materials such as fabrics. In particular, it is suitable for adhering cloths to each other or to cloths and flexible materials such as plastic films.

Claims (2)

(57) [Claims] 1. A polyurethane-based propolymer having a viscosity of 10,000 to 80,000 centipoise at 25 ° C. obtained by reacting a polyol containing polyoxytetramethylene-based diol as a main component with 1.2 to 2.4 times equivalent amount of a diisocyanate compound. A polyurethane adhesive composition containing 50 to 90% by weight and 10 to 50% by weight of a polystyrene oligomer having a molecular weight of 2000 or less, and having a viscosity at 100 ° C. of 500 to 6000 centipoise. 2. A first claim for use in a porous material.
Adhesive composition of paragraph.