JPS5958071A - Pressure-sensitive adhesive curable with moisture - Google Patents

Abstract

PURPOSE:To provide the titled adhesive giving excellent peeling strength to plastics, coated metals, etc. after complete curing, by compounding a polymer containing a carboxyl group with a polymer free of carboxyl group at a specific ratio, and adding a IIa-group metal oxide, etc. to the mixture. CONSTITUTION:The objective adhesive is prepared by using (A) a blended polymer obtaned by mixing (i) a polymer containing 0.2-25wt% of carboxyl group (e.g. acrylic acid-alkyl acrylate copolymer) with (ii) a polymer free from carboxyl group [preferably having a glass transition temperature (Tg) of -30- 0 deg.C] at a weight ratio of 1:(0.1-3) under essentially dried condition, and if necessary bonding (iii) a third substance to the mixture, and (B) an oxide of the IIa-group metal of the periodic table or a mixture of the oxides, as essential components. The amount of the component (B) is e.g. 1-200pts.wt. per 100pts.wt. of the component (i). USE:Pressure-sensitive adhesive tape, etc.

Description

[Detailed Description of the Invention] This invention provides pressure-sensitive adhesive properties in the bonding area M],
After bonding, it relates to a pressure-sensitive adhesive that can harden as it absorbs moisture, such as moisture, and in particular, when the adherend is a non-polar material such as plastic or painted metal, it is necessary to completely cure the pressure-sensitive adhesive. The purpose is to increase the subsequent peeling adhesive strength.

Conventionally, pressure-sensitive adhesives have been proposed that contain a carboxyl group-containing polymer and an acid of a group 11a metal of the periodic table or a mixture thereof in a dry state substantially free of moisture. The adhesive has the property of curing by absorbing moisture in the air due to the moisture absorption phenomenon Q4, which accelerates the crosslinking reaction.The curing reaction of such pressure-sensitive adhesives occurs naturally due to the absorption of moisture in the air. to harden to
It has the advantage of increased adhesive strength compared to conventional non-reactive pressure-sensitive adhesives, and is economical as it does not require any heating operation unlike thermosetting pressure-sensitive adhesives. It has significant technological advantages over time.

In other words, thermosetting pressure-sensitive adhesives require expensive heating equipment, which can pose a fire hazard or damage the adhered object, and the heating process is also time-consuming, so it is easier to use with finger pressure or an adhesive roll. The unique advantage of pressure-sensitive adhesives, such as being able to be attached to funerals, is not fully utilized.

Therefore, thermosetting pressure-sensitive adhesives are applied to sheets or films to make adhesive tapes, and are not suitable for insulation or wiring parts of electrical equipment that generates heat during use, such as generators, motors, or transformers. Comparatively, '1jI5J can be added, but it is difficult to heat it, or it is not possible to heat it.
It cannot be used for various purposes such as adhesive tiles, decorative plywood, or wallpaper. soil.

The moisture-curing type pressure-sensitive adhesive proposed above is an epoch-making curing method in that it can completely eliminate the drawbacks of thermosetting type adhesives.

However, when moisture curing is completed by the above method, the shear adhesive strength of the pressure sensitive adhesive is 20 to 30 9/cJ
However, it has been found that the behavior of the peel adhesion force is complex, and as curing progresses, a shortcoming often occurs in that it increases once and then rapidly decreases. In particular, polyethylene and polypropylene adherends have low-energy surfaces, and polyester, which is said to have a difficult adhesion surface,
It was found that the peel adhesion to surfaces such as acrylic-coated plates decreased significantly as curing progressed.

The present inventors investigated a method of increasing not only the shear adhesive strength but also the peel adhesive strength as the curing progresses in moisture-curing pressure-sensitive adhesives, without causing a slight decrease in carboxyl adhesive strength. By using a blend polymer of a polymer having a group and a polymer not having a carboxyl group, the above-mentioned corrugated body after curing is < +j
I found that j11 adhesive power (I found that I could get what I was worried about.

In other words, the present invention essentially uses a polymer containing carboxyl groups (M) with a carboxyl group content of 0.2 to 25 tm f7i'% and a polymer containing no carboxyl groups (in a dry state).
A hygroscopic curable material consisting of a blend polymer of B) in a small ratio of 1:0.1 to 1:3 and containing as an essential component an arsenic acid of Group 1 Ta of the Mendelev periodic table or a mixture thereof. A pressure sensitive adhesive is provided.

In this invention, a polymer having a carboxyl group (A
) is 1M with carboxyl groups in 16 molecules,
However, the number of carboxyl groups in the molecule is determined by the hardness of the metal oxide used, the hardness of the polymer base of the pressure-sensitive adhesive, and the hardness of the pressure-sensitive adhesive. ni dry r
It is necessary to take into consideration the compatibility with t4#1 fat when making a decision.

In general, the curing speed increases as the number of carboxyl groups increases, which is advantageous for the purpose of the present invention, and the hardness of the pressure-sensitive adhesive as a polymer base increases as the number of carboxyl groups increases. Compatibility with the adhesive resin decreases. Therefore, in order to maintain the balance between adhesive force and cohesive force as a pressure-sensitive adhesive before curing, it is necessary to use 02 to 25% carboxyl foundation in the polymer.
Generally, favorable results are obtained when 0.5 to 15 weight percent of IB is present.

The above carboxyl group-containing polymers include acrylic acid, methacrylic acid, itaconic acid, maleic acid,
When using a copolymer consisting of a monomer with a carboxyl group such as fumaric acid and other copolymerizable monomers such as butadiene, acrylonitrile, acrylic acid alkyl ester, and methacrylic acid alkyl ester. for,
For example, acrylic acid-acrylic acid alkyl ester copolymer, acrylic acid-methacrylic acid alkyl ester copolymer t1
) combination, methacrylic acid-acrylic acid alkyl ester copolymer-acrylic acid-butadiene copolymer, methacrylic acid-butadiene copolymer, acrylic acid-butadiene-a copolymer nitrile ternary copolymer (wood is preferably used) be done.

There are other natural rubbers. ) is a synthetic rubber treated with monothioglycolic acid to introduce a carboxyl group into the main chain, and the same rubber derivative can also be used for the neck. Co-1f of a monomer such as hydroxyalkyl (meth)acrylate or glycidyl (meth)acrylate having a functional group and a monorigid body indicated by nil
It may be a compound.

In addition, polymers that do not contain carboxyl groups (r31 is a single fi
A copolymer of monomers that do not contain carboxyl groups, natural rubber or synthetic rubber can be used.
It can also contain functional groups other than carboxyl groups, if desired. Hydroxy (meth)acrylate, glycidyl (
When using meth)acrylate as a monomer, it is more preferable to combine the polymer (B) and the polymer (A+ with the intervention of a third substance, since the amount of !2i1t of the polymer decreases.As the third substance, For example, polyfunctional incyanate, polyfunctional epoxy, peroxide, etc. can be used.This polymer (Bl is the glass transition temperature (T
y) is preferably in the range of -30°C to 0°C; if it exceeds 0°C, the initial adhesive strength will be low, and if it is lower than -30°C, the shear adhesive strength after moisture absorption and curing will be low. Undesirable.

Also, the mixing ratio of polymer (H) and polymer (B+) is 1
:0.1 to 1:3 is preferable, and when the ratio of the polymer (13) not containing a carboxyl group is lower than 0.1, the peel adhesion strength to the adherend due to curing is low. On the other hand, if the ratio of polymer (13) exceeds 3, the adhesive properties cannot be improved much due to moisture absorption and curing. A more preferable range is 1:0.25~
1; 2.

In addition, Mendelev is a metal oxide that does not harden in a dry state at room temperature or even under heating, but only functions as a crosslinking agent when absorbed by moisture, compared to the blend polymer of polymer (1) and polymer (R1). Oxides of metals belonging to Group +RA of the periodic table, that is, calcium, strontium, and barium, are most preferably used.These metal acid ratios are not limited to 14 or their mixtures, but include 774. It may also be a mixture with other materials such as alumina cement or portland cement.The oxides of the LRA group metals, such as magnesium and aluminum, exhibit similar behavior, but are more reactive. Since the crosslinking reaction proceeds gradually due to small amounts of water contained during the production of the pressure-sensitive adhesive, it is not recommended for practical use.

Addition of the above-mentioned Group Ia metal oxide: The amount of bone varies depending on the type of polymer having a carboxyl group, but it is generally best determined based on the curing speed and adhesiveness of the desired pressure-sensitive adhesive. Addition IJI of the metal depletion acid 1
FA is a polymer containing a carboxyl group (to) 100
It is possible to add between 1 and 200 parts by weight, but preferably 5 to 100 parts by weight.

As the adhesive resin, those having a softening point of 40° C. or higher among coumaron indene resins, petroleum resins, terpene resins, rosins, ester gums, etc. are preferably used. The additive amount of this adhesive resin varies depending on the adhesive resin and the type of polymer (, to) having a carboxyl group (,
l~) When 5 to 100 parts by weight, preferably 10 to 60 parts by weight, are added to 1 part by weight f, an old-fashioned improvement in peel adhesion strength is observed.

The pressure-sensitive adhesive of the present invention includes the carboxyl group-containing polymer (~) and the carboxyl group-free polymer (~).
The blended polymer with I3), the RA group oxide and the adhesive 1J/I fat are uniformly dissolved in an organic solvent by a known method. functions, and then moisture in the air,
Since the purpose is to sequentially exhibit the ability to naturally harden due to moisture absorption, each raw material used is dehydrated as much as possible to the extent that it contains virtually no free water. As the dehydration method, any dehydration operation such as heating, centrifugation, or reduced pressure may be performed, but a method using reduced pressure dehydration is effective in that it does not alter the quality of each raw material. In addition, the liquid raw material is preferably dehydrated using a desiccant such as calcium chloride (anhydrous) or silica gel.

In general, organic solvents for low molecular weight polymers are free water,
It is known to contain moisture in the form of hygroscopic water or conjugated water, with a water content ranging from 10 to 10%. In order to exert the function of this invention, dissociated water should be removed as much as possible, but it is not necessary to remove a small amount of adsorbed water or conjugated water; on the contrary, it is necessary to remove it at the beginning of bonding with the pressure-sensitive adhesive. It is effective in promoting a low degree of crosslinking reaction to improve cohesive strength.

The substance obtained as described above contains 1-moisture.

It is of course possible to further add compounding agents such as a partial crosslinking agent, a plasticizer, a stabilizer, a pigment, or a filler to the pressure-sensitive adhesive h11, if necessary.

The pressure-sensitive adhesive of this invention can be applied to one or both sides of a tape or sheet and dried to produce a pressure-sensitive adhesive tape, sheet or label. The tapes exhibit normal pressure-sensitive adhesive properties.

The conditions for drying and repeatedly removing organic solvents when producing such sensitive adhesive tapes are determined by whether even high heating conditions have no effect on the curing reaction of the pressure-sensitive adhesive or are affected by the humidity rule. 11η, ≦ is large, humidity 1! , t' or 30% R11 (
However, it is possible to apply it and dry it. This is because the curing speed of the pressure-sensitive adhesive of the present invention is clearly different when the humidity is low (below 30% R, Ij) and when the humidity is high above that. It is thought that the humidity is 30%
R, II, for a short time, for example 111 when the tape is drying.
Even if the degree of crosslinking reaction is low, IV (4) will cause the moisture absorption curing rate to be slow and the actual curing will hardly proceed.

On the other hand, if the tapes listed in -1- are stored for a long time, the curing reaction will hardly proceed if they are stored at a humidity of 15%, preferably at 10% R,I (or less). It is sealed together with a desiccant, and after use it absorbs moisture from the air and hardens, rapidly increasing its adhesive strength.
It is extremely suitable for applications requiring oral adhesion and Jf4 addition of adhesive strength after application without taking any special measures.

This invention will be further clarified by the following examples.

Note that the middle part of the example refers to the middle F scrap part.

Example 1 In a reaction vessel, 100 parts of phtyl methacrylate, 1 part of acrylic acid, 0.3 parts of benzoyl peroxide, and 22 parts of ethyl acetate were added.
When the copolymerization reaction was carried out after stirring for 6 hours while keeping the temperature Iw at 65°C in a nitrogen stream, the polymerization conversion rate was 9.
Polymer (・
~) () 1 ruhoquine group included 10 iT (@Vo)
A homogeneous solution containing 29.4 wt.

Also, 30 parts of butyl methacrylate, 7 parts of ethyl acrylate
A polymer (n) solution (polymer (Bla'♀ degree 29.8% by weight) was obtained in the same manner as in the case of polymer (2) using 0 parts of 2-hydroxyethyl acrylate and 3 parts of 2-hydroxyethyl acrylate.

The Ty of this polymer (111 was about -12°C, then the humidity was 30% R,H, the substance below) - 220 parts of the above polymer (A+ solution) and the polymer (1
1) Add 2 parts of toluene diisocyanate, 30 parts of Kumaron V 120 (manufactured by Nippon Steel Corporation) and 30 parts of 11 calcium acid (400 mesh) to a mixture of 110 parts of the solution and mix uniformly to make a pressure-sensitive adhesive, For the adhesion test, it was applied to a polyester film with a thickness of 25 μm to a dry thickness of 30/l, and dried at 120° C. for 5 minutes to prepare a pressure-sensitive adhesive tape.

Comparative Example 1 A copolymer consisting of 85 parts of butyl methacrylate, 15 parts of ethyl acrylate and 1 part of acrylic acid was prepared in Example 1.
2 parts of toluene diisocyanate, 30 parts of Coumaron V M (supra) and 30 parts of calcium oxide (400 mesh) were added, and a pressure-sensitive adhesive tape was prepared in the same manner as in Example 1. Created.

Example 2 100 parts of n-octyl acrylate, 10 parts of methacrylic acid, 03 parts of benzoyl peroxide, and 225 parts of ethyl acetate were poured into a reaction vessel, and the mixture was reacted in the same manner as in Example 1. When the polymerization reaction is carried out, the polymerization conversion rate is 96 tons
ri%, and polymers with carboxyl groups (H
A homogeneous solution containing 30% by weight of carboxyl bases (total of 9.1 m%) was prepared.

Next, a polymer (13) solution (polymer ("l 诧I!
0% by weight). 1 V of this polymer (13) was approximately -6°C.

Then, in a substantially dry state, the polymer (・＼)
165 parts of solution and 165 parts of polymer solution were mixed, and to this were added 0.5 parts of benzoyl peroxide, 30 parts of rosin (Rosin 3A manufactured by Arayo Forestry Chemical Co., Ltd.) and Portland cement (4 parts).
A uniform pressure-sensitive adhesive solution was prepared by adding 40 parts of 00 Metsuyu), and a pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 for use in an adhesion test.

Comparative Example 2 A copolymer consisting of 45 parts of n-octyl acrylate, 45 parts of 5ec-butyl acrylate, 10 parts of acrylonitrile and 50 parts of methacrylic acid was obtained in the same manner as the polymer of Example 1 in ethyl acetate. Ta. The same additives as in Example 2 were added to this and a pressure-sensitive external tape was prepared in the same manner as in Example 1.

Example 3 Acrylic acid-butyl acrylate-acrylonitrile terpolymer (acrylic acid 2.5
Weight%: Carboxy group content: 2.4% (carboxy group total) Commercially available acrylic rubber (trade name: Rheocoat) was used as a polymer, and 230 parts of ethyl acetate was added to 100 parts of this acrylic rubber and mixed uniformly. Dissolved (polymer (,
8) Agricultural content: 30% by weight).

Using 60 parts of loubutyl acrylate, 40 parts of vinyl acetate and 2 parts of glycidyl methacrylate, apply the same polymer CB+ solution (polymer (R) concentration 30% by weight) as the polymer (7~) of Example 1 using a brush. Obtained.

The T9 of this polymer (I'S) was approximately -26°C.

After mixing 99 parts of polymer (A+ solution) and 231 parts of polymer (I3) solution in a substantially dry state, 30 parts of Coumaron-rM (Coumaron indene resin manufactured by Fuji Steel) and 30 parts of barium acetate (400 mesh) were mixed. A uniform pressure-sensitive adhesive solution was obtained by adding 50% of the pressure-sensitive adhesive solution.A pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 for use in an adhesive force test.

Comparative Example 3 330 parts of the polymer solution of Example 3, Coumaron\
t 120 (+)iiili ) and 30 parts of barium oxide (400 mesh) were added and mixed uniformly to prepare a pressure-sensitive adhesive tape in the same manner as in Example 1.

The table shows the pressure sensitive adhesive tape sample pieces obtained in the above Examples and Comparative Examples under certain hygroscopic curing conditions (60°C,
This figure shows the oral change in peel adhesion strength under a humidity of 90% Rjl.

However, the peel adhesion strength (unit: 972 cm) is determined by pasting the sample tape on an acrylic resin plate and measuring 1 at 20°C.
The adhesive strength is shown when peeling is performed at 180° at a speed of 0 mm and 7 minutes.

As is clear from the handwritten results, Comparative Examples 1 to 3-6 ψ containing a polymer having a carboxyl group and an oxide of a metal of group 1RA of the periodic table or a mixture thereof.

In contrast, in Examples 1 to 3 according to the present invention, the peel strength of pressure-sensitive adhesives significantly decreases as the curing progresses, i.e., polymers with carboxyl groups. (B1,
! It can be seen that the peeling and splitting adhesive strength of the blended polymer of - and the metal hygroscopic pressure-sensitive adhesive gradually increases as the curing progresses and does not decrease.

Claims (1)

[Scope of Claims] (]) In the substantially dry state, carboxyl fund 1i
j Ka0.2-251'j iil efQ (7) Polymer (to 7) and polymer not containing carboxyl group (1
3) Moisture-hardening pressure-sensitive adhesive consisting of a blended polymer with weight: 1; Agent 11° (2) Glass transition temperature ('T') of polymer (+3)
The moisture-hardening pressure-sensitive adhesive according to claim (1), wherein g) is in the range of -30°C to 0°C.