JPH023489A - Reactive solventless polyurethane adhesive - Google Patents

Abstract

PURPOSE:To obtain a reactive solventless adhesive having excellent adhesive strength to various plastics and excellent durability by employing as a principal component a resin-forming compsn. comprising a particular prepolymer contg. active isocyanate groups and, added, thereto, a polyfunctional compd. CONSTITUTION:This polyurethane adhesive comprises as a principal component a resin-forming compsn. composed of a prepolymer having active isocyanate groups and a polyfunctional compd. As the prepolymer, use is made of one obtd. by reacting an org. polyisocyanate contg. a compd. of formula III in an amt. of at least 10wt.% with a polymer precursor comprising, in the principal chain molecule, branched structure units represented by formula I or II and having active hydrogeatoms at terminals thereof, in such proportions that the whole amt. of active isocyanate groups is in excess of that of the active hydrogenatoms. General formulation recipe can be applied to the above- mentioned adhesive as long as the purpose thereof is not impaired. In many cases, talc, titanium oxide, calcium carbonate, etc., may be pref. added.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an adhesive that exhibits good adhesion and durability to various adherends, particularly to various plastics.

(Prior Art) Various types of solvent-free polyurethane-based reactive adhesives using polyether-based or various polyester-based polyols have been invented.

However, conventional adhesives using polyols have low adhesion strength to various adherends, especially plastics, and have not been satisfactory. In particular, the adhesive strength of conventional adhesives to ABS resin, hard vinyl chloride resin, polycarbonate, and PRP is extremely low unless primer treatment is applied.

Therefore, surface treatment such as brimer treatment is required, and there are many problems such as a decrease in production efficiency and workability. Furthermore, there is a drawback in terms of durability performance, as the adhesive strength significantly decreases under high temperature and high humidity conditions. It is considered unsuitable for use as a so-called structural or heavy structural adhesive and is not in full-scale actual use.

(Problems to be Solved by the Invention) In view of the above-mentioned current situation, the present invention aims to obtain a solvent-free polyurethane-based reactive adhesive that has excellent normal adhesive strength and durability and is suitable for structural or semi-structural applications. With the goal.

(Means for Solving the Problems) The present inventors focused on the basic molecular structural unit of urethane adhesives, studied to fully demonstrate adhesive performance, and based on a polyester polymer with a specific structure, The present invention was accomplished by discovering a solvent-free polyurethane reactive adhesive based on a composition containing a specific polyfunctional compound. That is, conventional polyalkylene polyols, linear polylactones, and even linear diol residues and carbon atoms with 5 carbon atoms.
Compared to urethane adhesives based on polyester polymers containing the following branched diol residues as constituent units, the adhesive of the present invention has high normal adhesion strength and low temperature resistance to various adherends, especially various plastics. It has been found that it has excellent properties such as strength and durability (water resistance, heat resistance), and is therefore highly practical as an adhesive for structural or heavy structures.

The present invention provides a polyurethane adhesive mainly comprising a resin-forming composition comprising a prepolymer containing an active isocyanate group and a polyfunctional compound, in which the prepolymer has the following formula (1) or (II) in the main chain molecule. A polymer precursor having a branched structural unit represented by and containing active hydrogen at the terminal contains 10% by weight or more of a compound represented by the following (I[l),
The present invention is a solvent-free polyurethane-based reactive adhesive characterized by using an organic polyisocyanate reacted with the total active isocyanate groups in an excess amount relative to the total active hydrogen layer.

OCH*CHtCH(CHs)CH*CH*O(1)-
OCR,CH,CII(C1,)C1,CO-([)(
In the [[) formula, n is an integer of 1 or more, preferably 1 to 4, and a mixture of compounds in which n is 1 or more is preferable.

The prepolymer used in the present invention has a branched structural unit represented by the above formula (1) or (II) in the main chain molecule, and a polymer precursor having an active hydrogen at the terminal has a branched structural unit represented by the above formula (III). It can be obtained by reacting an organic polyisocyanate containing 10% by weight or more of the compound represented by the formula in such a proportion that the total active isocyanate groups are in excess of the total active hydrogen.

Examples of the above-mentioned precursors include those into which a structural unit represented by the above formula (1) or (It) is introduced, and an active hydrogen into which an isocyanate group can be introduced is placed at the end of the structural unit.

As long as the structural unit represented by the above formula (1) or ([[)] is introduced into the precursor skeleton, there is no restriction on the method of introduction. Particularly preferred are polyester types which are introduced by reaction with any dicarboxylic acid component. Polyester polyurethane, polycarbonate, etc. may be introduced. There is no particular restriction on the content of the structural unit represented by formula N) or (II) in the precursor, but it is usually used in an amount of 5% by weight or more, especially 10% or more by weight. .

Examples of the precursor containing the branched structural unit of the above formula (1) include dicarboxylic acid and 3-methyl-1,5-bentanediol, and if necessary, other types of polyfunctional polyols or polycarboxylic acids. The following examples include polyester polyols obtained by condensation polymerization.

There are no particular restrictions on the monomer diols that can be copolymerized, such as ethylene glycol, 1.4-butanediol, 1.6-hexanediol, 1.9-nonanediol, 1.10-decanediol, 1.12- Linear diols such as dodecane diol, branched diols such as propylene glycol and neopentyl glycol, diethylene glycol, and any mixtures thereof are used. Adhesion obtained by copolymerizing polyester polyols with carbon chain lengths of 5 to 12, such as 1.6-hexanediol, 1,9-nonanediol, 1゜10-decanediol, and 1.12-dodecanediol, among others. It is often used favorably from the viewpoints of coating properties, adhesive properties, water resistance, impact resistance, etc. of the agent. The dicarboxylic acid used in condensation polymerization is not particularly limited, and includes, for example, aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, and sepatic acid, terephthalic acid, isophthalic acid, phthalic acid,
Aromatic dicarboxylic acids such as 1,5-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, and 2,6-naphthalene dicarboxylic acid, and arbitrary mixtures thereof are used. Among them, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sepatic acid are often preferably used in view of the coating properties, adhesion properties, water resistance, impact resistance, etc. of the resulting adhesive.

An example of a precursor containing a branched structural unit of the above formula (III) is poly(β-methyl-δ-valerolactone) polyol. Specifically, it is obtained by ring-opening polymerization of β-methyl-δ-valerolactone using ethylene glycol, butylene glycol, and in some cases, a low-molecular polyhydric alcohol such as trimethylolpropane.

When the precursor is a polyester polyurethane type, the polyester polyol may have the same composition as the polyester polyol described above.

Although there is no limit to the molecular weight of the precursor, a number average molecular weight of 500 to 5000, particularly 800 to 20,000, is often used.

In the present invention, as the polyisocyanate used to obtain the prepolymer, a polyisocyanate represented by the above formula (III) is used. The polyisocyanate also facilitates maintaining proper viscosity of the prepolymer. Therefore, the adhesive obtained by using the polyisocyanate has satisfactory performance in all aspects such as coatability, adhesion, water resistance, and impact resistance. The polyisocyanate may be used alone or in combination with other isocyanates. The most preferred example of the present invention is a polyisocyanate containing 20% by weight or more of the compound of formula (III) above, with the remaining component being an aromatic diisocyanate. The mixing ratio should be appropriately set depending on the viscosity of the intended adhesive.

There are no particular restrictions on the other isocyanates to be mixed. Known aliphatic, ring group, or aromatic diisocyanates containing two isocyanate groups in the molecule are included. Typically, 4.4°-diphenylmethane diisocyanate (MDI), ) lye diisocyanate (T
D I ) or isophorone diisocyanate (IHDI
) is used.

In addition, p-phenylene diisocyanate, l,5-naphthylene diisocyanate, xylylene diisocyanate,
Hexamethylene diisocyanate, 4.4°-dicyclonoisocyanate, etc. can also be used. Among these, aromatic diisocyanates such as MDI or TDI are often preferably used in view of the coating properties, adhesion properties, water resistance, impact resistance, etc. of the resulting adhesive.

There are no particular restrictions on the production of the prepolymer, and methods commonly used for urethanization reactions can be applied. For example, the polymer precursor can be added to the polyisocyanate sequentially or simultaneously and reacted. At this time, in addition to the above precursor, a diamine compound, a thiol compound, etc. may be added simultaneously or sequentially to cause the reaction.

The viscosity of the prepolymer obtained in this way is usually 1 to 5,000 at 25°C, although there is no equivalent limit.
Furthermore, it is often used at 6 to 3000 poise.

In the present invention, a polyfunctional compound having an active hydrogen group refers to a prepolymer containing an active isocyanate group and a group (active hydrogen) that is reactive with the active isocyanate group in the same molecule, such as a 2 group, a carboxyl group, etc., or any of them. The formulation composition is illustrated.

Hydroxyl group-containing polyfunctional compounds include castor oil (ricinoleic acid triglyceride), natural polyols such as polysaccharides, polyfunctional poly-ε-caprolactone polyol, polyfunctional poly-β-methyl-δ-valerolactone polyol, polyfunctional polyester polyol, Multifunctional polycarbonate polyol, multifunctional polyester polyurethane polyol,
Examples include polyfunctional polypropylene polyol, polyfunctional polyethylene-propylene polyol, and the like. Among them, castor oil (ricinoleic acid triglyceride), polyfunctional poly-β
-Methyl-delta-valerolactone polyol, polyfunctional polyester polyol, polyfunctional polypropylene polyol, polyfunctional polyethylene-propylene polyol, etc., alone or in arbitrary mixed compositions thereof are often used in particular. A polyfunctional polyester polyol can be obtained by combining a polyfunctional polymerizable compound with the combination of raw materials used for producing the main chain-forming precursor.

Polyfunctional polyols such as lythritol, aconitic acid,
Polycarboxylic acids such as pyromellitic acid and trimellitic acid may be used alone or in any combination.

Examples of the amino group-containing polyfunctional compound include triethylenetetramine, piperazine, isophoronediamine, xylylenediamine, and the like.

These polyfunctional compounds can be used alone or in any combination, but preferably a hydroxyl group-containing polyfunctional compound or a combination of a hydroxyl group-containing polyfunctional compound and an amino group-containing polyfunctional compound. The polyfunctional compound preferably has a hydroxyl value within the range of 30 to too much. By appropriately adjusting the hydroxyl value, a reactive adhesive having excellent normal adhesive strength and durability suitable for structural or semi-structural applications can be obtained. More preferable hydroxyl value is 50-60
It is within the range of 0.

The viscosity of the thus obtained polyfunctional compound having an active hydrogen group is not limited, but it is usually used at a viscosity of 0.1 to 5,000 poise, and even 0.5 to 2,000 poise at 25°C. There are many. In addition, when using a polyfunctional compound whose average molecular number is usually 5000, the resulting polyfunctional compound has a particularly good balance between shear adhesive strength and peel adhesive strength.

The adhesive mainly composed of a prepolymer containing an active isocyanate group and a polyfunctional compound having an active hydrogen group used in the present invention can be used as is, but depending on the application, coating method, and required performance of the adhesive, A known catalyst can be added to the urethanization reaction. When adding it, there are methods such as adding it at the time of mixing the prepolymer and the polyfunctional compound, or adding it to both in advance, but usually it is often added to the polyfunctional compound in advance. Such catalysts include amines such as triethylamine, triethylenediamine, morpholine, diazabicycloundecene and its salts, dibutyltin dilaurate, trimethyltin hydroxide, stannic chloride, potassium oleate, stannous octoate, etc. Among these, amines such as diazabicycloundecene and its salts, and dibutyltin dilaurate are often used favorably in terms of adhesiveness, workability, durability, etc. The blending amount varies depending on the type of catalyst used, the composition of the prepolymer containing active isocyanate groups and the polyfunctional compound having active hydrogen groups, the required performance of the adhesive bonding site, etc. , 0OO1~l, especially o, oot~0.7
It is often used in parts by weight.

Blend 1 of a prepolymer containing a structural unit represented by the above formula (1) and an active isocyanate group in the main chain molecule and a polyfunctional compound having active hydrogen is based on the characteristic values of the prepolymer and the polyfunctional compound, and the characteristics of the adhesive. Although it varies depending on the required performance, in terms of adhesion, heat resistance, durability (water resistance, heat and humidity resistance, weather resistance), etc., the amount of polyfunctional compound per 100 parts by weight of the prepolymer is 10 to 500 parts by weight, especially 50 to 1 part by weight. 300
It is often used in juyobu. In the present invention, by setting the isocyanate group to 0.9 or more, a sufficient crosslinked structure can be formed and durability and water resistance can be increased. Further, by setting the corresponding ratio to 2 or less, foaming caused by reaction with water can be suppressed, and sufficient adhesive strength for practical use can be obtained.

Although the solvent-free polyurethane-based reactive adhesive according to the present invention can be used as is, there is no harm in applying known formulations used for ordinary polyurethane-based adhesives as long as the purpose of the present invention is not impaired. I can't help it.

Examples of such formulations include addition or grafting of phosphorus compounds, addition of evoquino compounds, silane coupling agents, antioxidants, ultraviolet absorbers, pigments, dyes,
Additions include inorganic fillers such as talc, titanium oxide, calcium carbonate, colloidal silica, glass beads, and various solvents. Among them, talc, titanium dioxide, calcium carbonate, etc. are often suitably contained.

Either heavy or light carbonate can be used. The additives such as calcium carbonate may be subjected to any surface treatment. Calcium carbonate whose surface has been treated with aliphatic carboxylic acid is often used for its workability and adhesive properties, calcium carbonate whose surface has been treated with rosin acid is frequently used because of its thixotropic properties, and calcium carbonate whose surface has been treated with stearic acid.

Cium is frequently used from the viewpoint of fluidity.

As titanium dioxide, both rutile type and anatase type can be used. Rutile titanium dioxide is advantageous in terms of heat resistance and weather resistance, and is particularly suitable as an additive for structural adhesives. Generally, the surface of the particles is often treated with an inorganic metal, and in particular, when the particles treated with aluminum are made of a prepolymer obtained from the polyisocyanate represented by the above formula (III),
It has good dispersibility and can be used in many ways.

The inorganic filler selected from the above has an average particle size of 0.03 to 15 μm, depending on its type, in terms of workability and adhesiveness.
m1 is preferably used in many cases, preferably from 0.03 to 5 μm. The amount of inorganic filler to be blended varies depending on the type of adherend, required performance, and bonding method, but is 5 to 75% by weight, preferably 15 to 60% by weight based on the adhesive.
is within the range of

They may be blended in a prepolymer containing an active isocyanate group, in a polyfunctional compound having an active hydrogen group, in both, or even when the two are mixed, but the present invention It can be arbitrarily selected as long as the purpose is not compromised.

For adhesion, an appropriate mixing method can be used depending on the workability of the process, such as manual stirring, stirring application using a dispenser, and the like.

The additive-free polyurethane-based reactive adhesive thus obtained is useful in a wide variety of applications, including construction, electrical appliances, toys, household goods, optical equipment, and automobiles.

(Example) The present invention will be specifically explained below using Examples.

Note that parts in the examples refer to weight unless otherwise specified.

(b) Adhesive operation and adhesive strength measurement Measured according to JIS K6850.

(b) Durability (high-temperature Toriya property) test After keeping the test piece in an atmosphere of 70°C and 95% RH for two weeks, the adhesive strength was measured, and the adhesive properties were evaluated according to the following 5-level evaluation based on the retention rate. Ta.

◎◎ Rura with a retention rate of 100% ◎ Those with a retention rate of 95% or more O Those with a retention rate of 85-95% Δ Those with a retention rate of 60-85% X The retention rate is 60% Example 1 Poly(β-methyl-δ
-valerolactone) glycol (PMVL-1) 28
．． 5 parts, 42.9 parts of MDI and 28.6 parts of polyisocyanate of formula (III) in the text under a nitrogen stream at 8 G.
An isocyanate-terminated prepolymer was synthesized by reacting under the conditions of 'C.

On the other hand, a trifunctional polyol with a terminal hydroxyl group obtained by polyaddition reaction of propylene oxide to glycerin, with a number average molecular weight of 330 (hereinafter abbreviated as PG-3), per mole of one with the same average molecular weight of 748 (hereinafter referred to as PG-3) (abbreviated as PC-7) were mixed at a ratio of 4 moles to prepare a polyfunctional compound having active hydrogen at the terminal. The hydroxyl value of the polyfunctional compound is 2
53 (mgKOH/g).

Dibutyltin dilaurate (hereinafter abbreviated as DBTDL) was added to the above polyfunctional compound as a urethanization catalyst at 1100%
0pp was added to form an active hydrogen-containing material.

The above isocyanate-terminated prepolymer and a polyfunctional compound were blended so that the ratio of (NGO)/(OH) was 1.2/1 to prepare an adhesive.

Various adherends were bonded using the adhesive, and the adhesive strength and high temperature and high humidity adhesive strength retention rate were measured. As a result, it shows good adhesive strength to various plastics, especially hard PVC and ABS resins, and also strongly adheres to polycarbonate, polymethyl methacrylate resin, Fr(P, etc.).In general, polyurethane adhesives It has very unique adhesive properties as it is said to be difficult to adhere to hard 270% ABS resin without primer treatment.It also has a high adhesive strength retention rate under high temperature and high humidity conditions, which is sufficient for practical use. The results are summarized in Table 1.

Example 2 PMVL-1 having a number average molecular weight of 2000 as in Example 1
An adhesive was prepared in exactly the same manner as in Example 1, except that poly(methylpentane sebacate) glycol (PMPS) having a number average molecular weight of 2,000 was used instead of . Thereafter, various adherends were adhered in the same manner as in Example 1. Table with results! It was shown to.

Example 3 After adding 23.3% by weight and 30.0% by weight of talc as an inert inorganic powder to the isocyanate-terminated prepolymer used in Example 1 and 30.0% by weight of calcium carbonate as a polyfunctional compound, various coatings were applied. The bodies were glued together and the adhesive strength was measured. As a result, the inclusion of inorganic powder increased the adhesive strength and provided very good adhesion to various plastics.

Moreover, the adhesive strength retention rate under high temperature and high humidity conditions is as high as 100%, which is the same as in Example 1, and it is possible to impart viscosity, thixotropy, etc.

The results are also shown in Table 1.

Example 4 Polyester diol has a molecular weight of 1500.
β-methyl-δ-valerolactone) glycol (PMV
L-2) was used to prepare an adhesive with the composition shown in Table I. Note that 11.5% by weight of rutile titanium dioxide was blended into the prepolymer.

The adhesion properties to various adherends were evaluated in the same manner as in Example 1.

The results are also shown in Table I. As shown in the table, adhesive strength equal to or higher than that obtained when using poly(β-methyl-δ-valerolactone) glycol with a number average molecular weight of 2000 was obtained, confirming the effect of the addition of inorganic powder. .

Comparative Example 1 A comparative adhesive was prepared and evaluated in the same manner as in Example 1, except that polypropylene ether glycol (PPG) having a number average molecular weight of 2000 was used as the polyester polyol. The adhesive strength to various adherends is low, and the high temperature and high humidity physical properties are also poor, so the effects of the present invention are clear.

Comparative Example 2 An isocyanate-terminated prepolymer was obtained in the same manner as in Example 1, except that a polyester diol with a number average molecular fi of 2000 obtained by polycondensation of ethylene glycol and adipic acid was used instead of PNOA-1 as the polyester polyol. , similarly evaluated plastic adhesives. The results are shown in the table, and although the adhesive strength is overall higher than that of PPG in Comparative Example 2, the retention rate of adhesive strength under high temperature and high humidity is extremely low, and the value is less than 60%. Therefore, the effects of the present invention are clear.

Margins below (effects of the invention) As explained above, according to the present invention, excellent durability and
A solvent-free polyurethane reactive adhesive having excellent normal adhesive strength suitable for structural or heavy structures can be obtained.

Patent applicant: Zensha Co., Ltd.

Claims (2)

[Claims] (1) In a polyurethane adhesive based on a resin-forming composition composed of a prepolymer containing an active isocyanate group and a polyfunctional compound, the prepolymer has the following formula (I) or (II) in the main chain molecule. An organic polyisocyanate containing 10% by weight or more of a compound shown in (III) below in a polymer precursor having a branched structural unit shown by A solvent-free polyurethane-based reactive adhesive characterized by using an adhesive that has been reacted in an excessive amount. -OCH_2CH_2CH(CH_3)CH_2CH_
2O-(I)-OCH_2CH_2CH(CH_3)
CH_2CO-(II)▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) However, n≧1 (2) The resin-forming composition contains calcium carbonate, talc,
Claim 1: The composition contains 5 to 75% by weight of at least one type of inorganic powder selected from the group consisting of titanium dioxide.
The solvent-free polyurethane reactive adhesive described in .