JPH093425A - Adhesive - Google Patents

Abstract

PURPOSE: To obtain an adhesive excellent in blocking resistance and the preservability in its aqueous solution state, thus useful as esp. a remoistening adhesive, consisting mainly of a new polyvinyl alcohol-based resin copolymerized with each specific two kinds of modifying components. CONSTITUTION: This adhesive consists mainly of a polyvinyl alcohol(PVA)-based resin (pref. 75mol% or higher in degree of saponification) copolymerized with (A) 0.1-10mol% of an N,N-di-branched alkylacrylamide of formula I [R1 is H or methyl group; R0 is of formula II (R2 to R4 are each H, an alkyl or aryl group; where, at least two of them are not H, and the number of carbon atoms for R2 to R4 totals >=4; (n) is 1-3)] (pref. N,N-diisobutylacrylamide) and (B) 0.1-10mol% of a hydrophilic group-bearing ethylenic monomer (e.g. ethylenic unsaturated carboxylic acid such as acrylic acid or a salt thereof). This PVA- based resin is normally obtained by saponification of a copolymer obtained by copolymerization between the components A and B and a vinyl ester (pref. vinyl acetate).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive using polyvinyl alcohol (hereinafter abbreviated as PVA), and more specifically, to a blocking resistance when a novel PVA resin is used as a rewetting adhesive. Excellent adhesive.

[0002]

2. Description of the Related Art Conventionally, PVA has been used as a rewetting adhesive for packaging tape, various labels, stamps, stamps, shoji paper,
It is used as a backing paste for wallpaper, fusuma paper, posters, etc., or as an aqueous solution as it is, as an adhesive for various packaging such as cardboard and bag making, and as an office glue. Furthermore, as a hot melt adhesive, bookbinding, bag making, box making, packaging, woodworking, shoe making,
It is used in various adhesives for applications such as fibers.

[0003]

SUMMARY OF THE INVENTION However, PVA
When used for adhesive, in rewetting adhesive,
Blocking of the base material after applying the PVA to the base material, and blocking of the hot melt adhesive during storage in the form of pellets, powders, etc. become a problem, and further rewetting adhesive, pressure sensitive adhesive, etc. In the adhesive used in the form of
There is often a problem also in its storage stability (blocking resistance further decreases when stored for a long time), and a PVA-based resin adhesive excellent in blocking resistance and storage stability has been desired. Of.

[0004]

Means for Solving the Problems As a result of intensive studies in view of such circumstances, the present inventor has found that a branched alkyl acrylamide (A) represented by the following chemical formula 1 is used as a modifying component.
0.1 to 10 mol% (preferably 0.1 to 5 mol%) of an ethylenic monomer having a hydrophilic group (preferably at least one kind of ethylenically unsaturated carboxylic acid or a salt thereof) (B) is added. The present invention was found to be excellent in blocking resistance and storage stability when a novel PVA-based resin copolymerized by mol% (preferably 0.1 to 5 mol%) is used for an adhesive, and the present invention has been completed.

Embedded image Here, R ₀ is shown in Chemical formula 2.

Embedded image (However, n is 1 to 3 and R ₁ is hydrogen or a methyl group.
R _{2 to} R ₄ are hydrogen, an alkyl group or aryl
Each represents a group, and at the same time two or more are not hydrogen but R
The total number of carbon atoms of _{2 to} R ₄ is 4 or more. )

Hereinafter, the present invention will be described in detail. The modified PVA (hereinafter sometimes simply referred to as modified PVA) -based resin of the present invention contains the (A) and (B) units as essential components as described above, and the (A) unit is represented by the above Chemical Formula 1. N, N-di-branched alkyl acrylamide components R _{1 to} R ₄
Of the above-mentioned functional groups, wherein the number of carbon atoms of the functional groups of R _{2 to} R ₄ is less than 4, the stability of the modifying group during saponification, the storage stability of the aqueous solution when used for a rewetting adhesive, etc. Bad
The carbon number is preferably 4 to 16.

The copolymerizable monomer containing the (A) unit is N, N-diisobutylacrylamide,
N, N-di (2-ethylhexyl) acrylamide,
Examples thereof include N, N-diisoamylacrylamide, N, N-diisobutylmethacrylamide, N, N-di (2-ethylhexyl) methacrylamide, and N, N-diisoamylmethacrylamide, and preferably N, N-
Diisobutyl acrylamide is preferably used. Examples of the copolymerizable monomer containing the unit (B) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, aconitic acid, fumaric acid, maleic acid monoester, and itaconic acid monoester. Examples thereof include esters, citraconic acid monoesters, fumaric acid monoesters, maleic anhydride, itaconic anhydride, citraconic anhydride, and salts thereof.

Usually, in order to produce the modified PVA-based resin of the present invention, a vinyl ester-based copolymer obtained by copolymerizing (A) and (B) with a vinyl ester (C) is saponified.
Examples of (C) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, and the like, and vinyl acetate is preferable from the economical viewpoint.

With respect to the ratio of each unit of the modified PVA-based resin, the N, N-di-branched alkyl acrylamide unit (A) shown in Chemical formula 1 above is 0.1 to 10 mol%, preferably 0.1 to 5 mol%. Mol%, 0.1-10 mol% of the ethylenic monomer (B) having a hydrophilic group, preferably 0.1-
It is suitable that the total amount of 5 mol%, the vinyl ester unit (C) and the vinyl alcohol unit (D) is 80 to 99.8 mol%. The degree of saponification (the ratio of the vinyl alcohol unit (D) to the total amount of the vinyl ester unit (C) and the vinyl alcohol unit (D)) is not particularly limited, but when the formed film is water-soluble. 70 mol%
It is preferably at least above, and particularly preferably at least 75 mol%.

The degree of polymerization of the modified PVA resin used in the present invention is not particularly limited, but is preferably 10 to 2,500, more preferably 300 to 2,000, and if the degree of polymerization is less than 100, the adhesiveness decreases, and conversely 2,500. If it exceeds, the viscosity of the PVA aqueous solution increases and the workability of the solution adhesive tends to be poor.

Next, the method for producing the modified PVA resin of the present invention will be described. The modified PVA-based resin of the present invention comprises an N, N-di-branched alkyl acrylamide monomer having a specific structural unit represented by the above Chemical Formula 1, at least one ethylenically unsaturated carboxylic acid or salt thereof, and a vinyl ester. It is obtained by saponifying the copolymer of.
The copolymerization reaction can be arbitrarily selected from known polymerization methods in radical polymerization, such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc., but solution polymerization is preferred from the industrial viewpoint.
Further, any method such as batch polymerization and continuous polymerization can be adopted. There are no particular restrictions on the method of charging the monomers during the polymerization, and any method such as batch charging, divided charging and continuous charging may be adopted, but branched alkyl acrylamide and ethylenically unsaturated carboxylic acid or salt thereof may be used as PV.
The divided charging method or the continuous charging method is advantageous in that it can be uniformly introduced into the A molecule.

As a catalyst for the copolymerization, known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauryl peroxide, and low-temperature catalysts such as azobisdimethylvaleronitrile and azobismethoxydimethylvaleronitrile. An active radical catalyst or the like is used. Further, the reaction temperature is not particularly limited and is appropriately selected from the range well known to those skilled in the art.
In such polymerization, other unsaturated monomers copolymerizable with the monomers other than the above three components, such as alkyl vinyl ether, methacrylamide, ethylene, propylene, α-hexene, unless the purpose of the present invention is impaired, α
-Olefins such as octene, α-dodecene, α-octadodecene, nitriles such as acrylonitrile and methacrylonitrile, alkyl acrylates, alkyl methacrylates, alkyl crotonic acid esters, dialkyl maleates, dialkyl itaconic acid, citracone A small amount of acid dialkyl ester, fumaric acid dialkyl ester and the like may be copolymerized.

The copolymer obtained by such a method is then saponified. As the saponification method, any method such as kneader saponification, continuous saponification, and pearl saponification can be adopted. In the saponification step, the residual monomer is expelled as necessary, and then saponification is performed according to a conventional method. To be done. Examples of the catalyst used for saponification include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate, alkali catalysts such as alcoholate, sulfuric acid, hydrochloric acid and the like. An acid catalyst is used.

The saponification reaction temperature is not particularly limited and is usually selected from the range of 10 to 60 ° C., preferably 20 to 50 ° C., and the saponification reaction is carried out for 5 to 240 minutes. The target modified PVA-based resin is obtained by neutralizing, washing with alcohol, etc., if necessary, and drying. Next, an adhesive using the obtained modified PVA-based resin will be described. The PVA-based resin can be used for various adhesives such as rewetting adhesives, hot-melt adhesives, pressure-sensitive adhesives, etc., in addition to general adhesives in which the resin is made into an aqueous solution, but it has blocking resistance. Are very useful as rewetting adhesives and hot melt adhesives, and will be described in more detail.

First, when used as a rewetting adhesive,
After the above PVA-based resin is made into an aqueous solution, it is applied to a base material such as gum tape or stamp and dried. At this time, alcohols such as methanol and ethanol and glycols such as ethylene glycol, propylene glycol, polyethylene glycol and glycerin may be added, if necessary. The coating can be performed by a known method such as a gravure coater, a reverse roll coater, an air knife coater, and a spray. It is also possible to form a rewetting adhesive layer by hot-melt coating.

When used as a hot melt adhesive, usually 100 parts by weight of the above PVA resin is used as a plasticizer (glycols such as ethylene glycol, propylene glycol, polyethylene glycol and glycerin, and urea derivatives such as ethylene urea). 5 to 50 parts by weight of hydrophobic resin (ethylene-vinyl acetate copolymer, phenol resin, styrene resin, polyester resin,
5 to 60 parts by weight of a polyamide resin, etc. is blended,
Furthermore, well-known additives for hot-melt adhesives such as hydroxy fatty acids, rosins, rosin esters, pinene-based polymers, hydrogenated petroleum resins, hydrocarbon resins, antioxidants, lubricants, fillers, and colorants. , Fragrance, stabilizer and the like are blended. The coating is carried out by a known hot melt coating machine such as roll, die, nozzle, lip, etc., which can be used for binding bookbinding, packaging, woodworking, adhesion of fibers, etc. In wet adhesive and hot melt adhesive applications, it has excellent blocking resistance after coating, and in rewetting adhesive applications it has excellent storage stability in the aqueous solution state (blocking resistance after long-term storage. There is no decrease in sex), which is very useful. The rewetting adhesive and the hot-melt adhesive have been described above, but the present invention is not limited to these, and a general aqueous solution adhesive, a pressure-sensitive adhesive,
It goes without saying that it can be used for various adhesives such as fast-curing (honeymoon) adhesives.

[0016]

[Operation] Since the adhesive of the present invention uses a specific modified PVA-based resin, it has excellent blocking resistance, and also has excellent storage stability in an adhesive in the form of an aqueous solution. It is very useful in various adhesive applications such as mold adhesives, rewetting adhesives and hot melt adhesives.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, “%” and “part” mean on a weight basis unless otherwise specified. (Production of modified PVA-based resin) A polymerization vessel equipped with a reflux condenser, a dropping funnel and a stirrer was charged with 1000 parts of vinyl acetate and 1500 parts of methanol, and the temperature was raised under a nitrogen stream while stirring to raise azobisisobutyrate at 62 ° C. A solution of 0.4 parts of ronitrile dissolved in 19.6 parts of methanol was added to initiate polymerization. From the polymerization start point, 8.0 parts of monomethyl maleate and N, N-diisobutylacrylamide 2
Polymerization was carried out while continuously dropping 61.2 parts of a methanol solution in which 2.6 parts were dissolved for 5 hours, and the polymerization was terminated when the conversion rate of vinyl acetate was 50%. Then, the unreacted vinyl acetate monomer was removed out of the system by a method of blowing methanol vapor to obtain a methanol solution of the copolymer. Then, the solution was diluted with methanol to adjust the concentration to 30% and charged in a kneader, and sodium hydroxide was added to neutralize while keeping the solution temperature at 35 ° C.

To this, sodium hydroxide was further added in an amount of 30 mmol with respect to the vinyl acetate unit in the polymer and kneaded. As the saponification reaction proceeded, a saponified product was deposited and finally became a particulate form. The resulting modified PVA-based resin was filtered, washed well with methanol, and dried in a hot air drier to obtain the desired product. The resulting modified PVA-based resin was extracted and washed with methanol using a Soxhlet extractor, and the modification degree with N, N-diisobutylacrylamide was analyzed by ¹ H-NMR. As a result, the modification degree was 2.0 mol%. . Further, the degree of modification of monomethyl maleate was analyzed by acid content determination by titration of the copolymer before saponification, the degree of modification was 1.0 mol%, and the degree of saponification of the modified PVA-based resin was The amount of alkali consumption required for the hydrolysis of the residual vinyl acetate unit was analyzed to be 90 mol%. The viscosity of the 4% aqueous solution of this modified PVA-based resin measured by a B-type viscometer is
The polymerization degree was 500 at 5.6 cps / 20 ° C.

Example 1 A 30% aqueous solution of the above-mentioned modified PVA-based resin was prepared, coated on a surface of a high-quality paper with a bar coater to a dry thickness of about 10 μm, and dried. Two sheets of the coated paper were prepared and stacked so that the coated surface and the other surface were in contact with each other and 10 g /
A load of cm ² was applied, the mixture was allowed to stand at 20 ° C. and 65% RH for 5 hours, the blocking property (I) was examined, and evaluated as follows. ○ --- There is no blocking at all. (Triangle | delta) -There is some blocking and there is resistance at the time of peeling. × −−− Blocking is remarkable and material destruction occurs during peeling.

Further, after the above PVA aqueous solution was left at 40 ° C. for 1 month, the blocking property (II) was examined in the same manner and evaluated in the same manner. In addition, the above-mentioned modified PVA-based resin 1
00 parts, 25 parts of glycerin, 35 parts of terpene phenolic resin, and 40 parts of 12-oxyoctadecanoic acid were charged into a melting can and melt-mixed at 170 ° C to obtain a hot melt adhesive. The adhesive was heated and melted to prepare a sample having a thickness of 100 μm, two samples were stacked, a load of 100 g / cm ² was applied, and the sample was left at 20 ° C. and 65% RH for 5 hours,
The blocking property (III) was examined and evaluated in the same manner as above.

Examples 2 to 7 and Comparative Examples 1 to 8 Copolymerization with vinyl acetate (in Comparative Example 8 in the same manner as in the above (Production of Modified PVA Resin)) with the components and charging amounts shown in Table 1. , Without adding a modifying monomer) and saponification to produce various modified PVA-based resins shown in Table 2,
Using the PVA-based resin, the blocking states (I) to (III) were evaluated in the same manner as in Example 1. Table 3 shows the evaluation results of the examples and comparative examples.

[0022]

[Table 1] Type of monomer copolymerized with vinyl acetate, charged amount and polymerization rate (A) Monomer (B) Monomer polymerization rate Species Charged amount Species charged amount (%) (mol%) ( Mol%) Example 1 D-i-BAAm 2.0 3M 1.0 50 〃 2 D-i-BAAm 2.0 3M 1.0 50 〃 3 D-i-BAAm 8.0 3M 4.0 46 〃 4 D-i-BAAm 0.5 3M 0.5 54 〃 5 D-i-BAAm 2.0 Itaconic acid 1.0 52 〃 6 D-i-PAAm 2.0 3M 1.0 54 〃 7 D-EHAAm 2.0 3M 1.0 46 Comparative Example 1 D-i-BAAm 2.0 −−− 50 〃 2 Nn-OAAm 2.5 3M 1.0 47 〃 3 VeoVa-10 1.0 AS 1.0 55 〃 4 VeoVa-10 3.0 Itaconic acid 1.0 50 〃 5 MRM 3. 0 --- 55 〃 6 --- AMPS 2.0 55 〃 7 --- 3M 1.0 60 〃 8 --- --- --87

Note) The charged amount represents a charged mole fraction (mol%) of each of the monomers (A) or (B) with respect to the total charged amount of the monomers. Abbreviations are as follows. D-i-BAAm; N, N-diisobutyl acrylamide D-i-PAAm; N, N-diisopentyl acrylamide D-EHAAm; N, N-di (2 ethylhexyl) acrylamide Nn-OAAm; N-n- Octyl acrylamide 3M; monomethyl maleate AS; sodium allyl sulfonate MRM; mono (diisopropylmethyl) malate VeoVa-10; monomer shown by the following chemical formula 3

Embedded image _{(Wherein, R 1, R 2, R} 3 is R ₁ is hydrogen or an alkyl radical, R
The total number of carbon atoms of ₂ , R ₃ is 10 on average. ) AMPS; sodium N-sulfoisobutylene acrylamide

[0024]

TABLE 2 content of the content of denatured P V A saponification degree (A) the monomer (B) monomer of 4% Viscosity (mol%) (mol%) (mol%) (cps) Example 1 90 2.0 1.0 5.6 〃 2 80 2.0 1.0 8.0 〃 3 85 7.7 4.0 5.9 〃 4 90 0.5 0.5 4.9 〃 5 75 2.0 1.0 10.1 〃 6 90 2.0 2.0 1.0 5.1 〃 7 75 2.0 2.0 1.0 6.9 Comparative example 1 90 2.0-5.8 〃 2 85 2.0 1.0 7.1 〃 3 75 0.8 9.1 9.1 〃 4 90 2.0 2.0 1.0 11.1 〃 5 90 90 2.0-6.1 6.1 〃 6 90 − 2.0 5.8 〃 7 90 − 1.0 7.1 〃 8 90 − − 5.5

[0025]

[Table 3]

[0026]

Since the adhesive of the present invention uses a specific modified PVA-based resin, it has excellent blocking resistance, and further has excellent storage stability in an aqueous adhesive.
It is useful in various adhesive applications such as general aqueous solution adhesives, rewetting adhesives, hot melt adhesives, pressure-sensitive adhesives, and quick-setting (honeymoon) adhesives, especially rewetting adhesives and hot melt adhesives. Very useful for

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Claims (2)

[Claims] 1. An N, N-dibranched alkyl acrylamide (A) represented by the following chemical formula 1 is 0.1 to 10 mol%, and an ethylenic monomer having a hydrophilic group (B) is 0.1 to 10: An adhesive comprising a polyvinyl alcohol-based resin as a main component, which is obtained by copolymerization by mol%. Embedded image Here, R ₀ is shown in Chemical formula 2. Embedded image (However, n is 1 to 3 and R ₁ is hydrogen or a methyl group.
R _{2 to} R ₄ are hydrogen, an alkyl group or aryl
Each represents a group, and at the same time two or more are not hydrogen but R
The total number of carbon atoms of _{2 to} R ₄ is 4 or more. ) 2. The adhesive according to claim 1, wherein the ethylenic monomer (B) having a hydrophilic group is at least one kind of ethylenically unsaturated carboxylic acid or a salt thereof.