JP2554928B2 - Hot melt adhesive composition and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot melt adhesive composition, and more particularly to a hot melt adhesive comprising an ethylene-vinyl acetate copolymer, a wax and a rosin-based tackifying resin. The present invention relates to improvement of a tackifying resin in a composition.

The hot-melt adhesive is solid at room temperature and melts by heating to form a liquid, which is applied to various base materials for bonding. Then, by cooling, it solidifies again to develop an adhesive force.

Since this hot melt adhesive has 100% solids and contains no volatile components, it does not shrink when solidified,
Also, since it does not contain volatile solvents, there is no risk of fire,
Further, since it is solidified by simply cooling, it has many advantages such as short set time and easy handling, and is widely used in various fields such as bookbinding, packaging, and woodworking.

2. Description of the Related Art Conventional hot melt adhesive compositions of this type include an ethylene-vinyl acetate copolymer (EVA) as a base polymer, a wax as a viscosity modifier, and a rosin-based resin as a tackifier. A mixture is used.

As the tackifier, in addition to rosin-based resins, terpene-based resins and various petroleum resins may be used, but cold rosin-based resins are excellent in terms of cold resistance, adhesive strength, and the like. Widely used.

However, when this rosin-based resin is used as a tackifier, it cannot be said that the heating stability is always good. Although there have been known solutions to increase the stability of rosin-based resins by asymmetry or hydrogenation, or to add antioxidants, they have not been sufficient.

Further, as a modified version of this rosin-based tackifying resin, the hot melt adhesive composition described in JP-A-60-28476 is known. This hot melt adhesive composition is used as a tackifying resin for partial fumarization and / or
Alternatively, a partially maleated disproportionated rosin ester is used. Thus, the hot-melt adhesive composition shown here is excellent in heat stability without being skinned, colored, or turbid for 24 hours or more in a molten state by heating to 200 ° C. It is said that.

Problems to be Solved by the Invention As described in the above publication, heat stability is one of the extremely important properties in a hot melt adhesive composition. It is considered that one effect is that the hot melt adhesive composition maintains stability for 24 hours. However, when considering the severe use condition of the hot melt adhesive composition, with this degree of heating stability,
Not quite enough yet.

Put a large amount of hot melt adhesive composition in a molten state,
In the case of dipping various base materials on this or coating with a drum applicator, the hot melt adhesive composition must be consumed within 24 hours, that is, within one day. However, in the process described above,
In many cases, the amount of hot melt adhesive composition consumed per day is less than the accumulated amount, and the stability of 24 hours is not enough.

When using a nozzle applicator or the like, since the hot melt adhesive composition passes through a thin nozzle, the nozzle may be clogged even if there is a very small amount of condensed matter, which may hinder the work. Therefore, higher heating stability is required.

The present invention has been made in view of such circumstances, has an extremely high heating stability, does not cause skinning or turbidity even after 100 hours, extremely stable hot melt adhesive composition and The purpose is to provide a method for producing the same.

Means for Solving the Problems Thus, the hot-melt adhesive composition of the present invention is a hot-melt adhesive composition comprising an ethylene-vinyl acetate copolymer, a wax and a tackifying resin as main components, wherein the tackifying resin is Is a polyhydric alcohol ester of asymmetric asymmetric rosin partially added with acrylic acid.

Further, in this hot melt adhesive composition, it is preferable that the rosin, which is a raw material of the tackifying resin, is purified.

Further, in this hot melt adhesive composition, the addition ratio of acrylic acid to the raw material rosin in the tackifying resin is preferably 2.3 to 45 mol%, and the softening point of the tackifying resin is preferably 100 to 140 ° C.

Further, the method for producing a hot melt adhesive composition according to the present invention, rosin is subjected to an addition reaction of acrylic acid, an asymmetric reaction, and an esterification reaction with a polyhydric alcohol,
The obtained rosin-based resin is mixed with an ethylene-vinyl acetate copolymer and a wax.

The EVA and wax in the present invention can be appropriately selected and used from the commercially available base polymers and viscosity modifiers for hot melt adhesive compositions.

Further, the tackifying resin needs to be an asymmetric rosin partially added with a polyhydric alcohol ester of acrylic acid.

Further, this tackifying resin can be obtained by adding acrylic acid to rosin, then asymmetrically treating this, and then carrying out an esterification reaction with a polyhydric alcohol.

As the raw material rosin for this tackifying resin, gum rosin, wood rosin or tall oil rosin can be used.

Acrylic acid is partially added to the raw material rosin, and the addition rate is suitably 2.3 to 45 mol% with respect to the raw material rosin. More preferably, it is about 4 to 25. When the addition rate of acrylic acid is low, it is difficult to obtain a resin having a high softening point and the adhesive strength becomes insufficient, and when the addition rate is too high, the compatibility of the obtained tackifying resin with EVA is poor.

The addition reaction of acrylic acid to the raw material rosin can be performed by a known method. For example, by heating and melting the raw material rosin,
By adding acrylic acid to this, a Diels-Alder type addition reaction can be performed.

The asymmetric reaction of rosin is also performed by a known method. For example, it can be carried out by adding acrylic acid to the raw material rosin and then adding the asymmetric catalyst under heating and melting. Examples of the asymmetric catalyst include noble metals such as palladium carbon, nickel and platinum, iodine compounds such as iodine and iron iodide, and sulfur compounds such as sulfur dioxide and iron sulfide.

The asymmetric reaction is 0.5% of conjugated dienoic acid in rosin.
It is preferable to carry out until the following. If the asymmetric reaction is insufficient, the heating stability is insufficient.

The polyhydric alcohol to be esterified with rosin in the present invention is preferably a trihydric or higher alcohol in consideration of the molecular weight, softening point and the like of the obtained rosin resin. Specific examples include glycerin, diglycerin, pentaerythritol, dipentaerythritol, and the like, with glycerin or pentaerythritol being particularly preferred.

The esterification reaction can be carried out in the same manner as a usual rosin esterification reaction. That is, the rosin and alcohol can be mixed and reacted while heating and melting while dehydrating, or can be melted in a solvent and reacting while dehydrating in the presence of a suitable catalyst. The ratio of rosin to alcohol is 1% of carboxylic acid in the acrylic acid adduct of rosin.
It is appropriate that the hydroxyl group in the alcohol is about 1 equivalent to the equivalent.

The production reaction sequence of the tackifying resin in the production method of the hot melt adhesive composition of the present invention is not particularly limited.
In short, the raw material rosin is produced by carrying out three reactions of a reaction of adding acrylic acid, an asymmetric reaction for the acrylic acid adduct, and an esterification reaction with a polyhydric alcohol. The addition reaction of 1 must be performed before the asymmetric reaction, but the time for performing the esterification reaction is not limited.

The mixing ratio of EVA, wax and tackifying resin in the present invention is not particularly limited. Depending on the use and purpose of use of the hot-melt adhesive, the mixing ratio may be approximately the same as the mixing ratio of the three in the conventional ordinary hot-melt adhesive, and can be arbitrarily determined.

Example Hereinafter, an example of the present invention will be described.

Preparation of rosin-based resin Example 1 100 parts by weight of gum rosin was charged into a four-necked flask equipped with a stirrer, a drainage tube with a cooling tube, a thermometer and a nitrogen injection tube, and heated to 180 ° C. under a nitrogen atmosphere to melt with stirring. did. Next, 1 part by weight of acrylic acid (4.6 mol% relative to rosin) was added dropwise at the same temperature, the temperature was raised to 200 ° C., and the acrylic acid addition reaction was carried out under reflux.

Further, 0.07 part by weight of palladium carbon (5% Pd-C) was added, the temperature was raised to 260 ° C, and the asymmetric reaction was carried out until the conjugated dienoic acid became 0.5% or less.

Then, after melting the catalyst to remove the catalyst, the product 100
One part by weight and 11.1 parts by weight of pentaerythritol were charged into the reactor, and esterification was carried out at 280 ° C. for 15 hours in a nitrogen stream to obtain a rosin resin.

The softening point of this resin was 110 ° C., the acid value was 15.8, and the Gardner color tone was 7.

Example 2 The amount of acrylic acid added to gum rosin was 3.5 parts by weight (16.1 mol% based on rosin), the amount of pentaerythritol added was 12.3% by weight, and otherwise the same operation as in Example 1 was repeated to obtain a rosin resin. Obtained.

The softening point of this resin was 118 ° C., the acid value was 15.8, and the Gardner color tone was 7.5.

Example 3 The amount of acrylic acid added to gum rosin was 4.9 parts by weight (based on rosin 22.6 mol%), the amount of pentaerythritol added was 13.0% by weight, and otherwise the same operation as in Example 1 was carried out to obtain a rosin resin. Obtained.

The softening point of this resin was 125 ° C, the acid value was 15.6, and the Gardner color tone was 7.5.

Example 4 In place of pentaerythritol in Example 3, 11.8 parts by weight of glycerin was added, and otherwise the same operation as in Example 3 was carried out to obtain a rosin resin.

The softening point of this resin was 110 ° C., the acid value was 8.0, and the Gardner color tone was 6.

Example 5 In a 2 liter volume distillation flask equipped with a thermometer and an air cooling tube,
1200 g of gum rosin was charged, the temperature was raised to 180 ° C. in a nitrogen atmosphere to completely dissolve the raw material gum rosin, and then cooled to 120 ° C. Next, the system was depressurized to 3 mmHg, the temperature in the flask was raised to 280 ° C., and the pressure was distilled under reduced pressure.
%) Was obtained. The distillation residue was 3.8% and the loss was 2.0%.

The purified rosin obtained had a softening point of 76 ° C. and an acid value of 170.

In the operation of Example 1, the purified rosin was used instead of gum rosin, the addition amount of acrylic acid was 3 parts by weight (13.7 mol% relative to rosin), the addition amount of pentaerythritol was 12.3 parts by weight, and the others were The same operation as in Example 1 was carried out to obtain a rosin resin.

The softening point of this resin was 118 ° C., the acid value was 15.8, and the Cardner color tone was 6.

Example 6 The amount of acrylic acid added to the purified rosin was 4.9 parts by weight (based on rosin 22.6 mol%), the amount of pentaerythritol added was 11.8% by weight, and otherwise the same as in Example 5, except that the rosin resin was used. Got

The softening point of this resin was 126 ° C., the acid value was 15.5, and the Cardner color tone was 6.

Example 7 The same operation as in Example 6 was carried out except that glycerin was used instead of pentaerythritol as the polyhydric alcohol.
A rosin resin was obtained.

The softening point of this resin was 112 ° C., the acid value was 7.0, and the Cardner color tone was 5.5.

Comparative Example 1 100 parts by weight of gum rosin was charged into the same reaction apparatus as described in Example 1, heated to 180 ° C. under a nitrogen atmosphere, and stirred and melted. Then, 3.0 parts by weight of maleic anhydride (10.1 mol% with respect to rosin) was added, and the temperature was raised to 220 ° C. to carry out the maleation reaction.

Further, 0.07 part by weight of palladium carbon (5% Pd-C) was added, the temperature was raised to 280 ° C., and the asymmetric reaction was carried out until the conjugated dienoic acid became 0.5% or less.

After melting the catalyst to remove the catalyst, the product 10
0 part by weight and 11.9 parts by weight of pentaerythritol were charged into the reactor, and esterification was carried out at 280 ° C. for 15 hours under a nitrogen stream to obtain a rosin resin.

The softening point of this resin was 110 ° C., the acid value was 15.8, and the Gardner color tone was 7.

Comparative Example 2 In place of maleic anhydride in Comparative Example 1, 2.5 parts by weight of fumaric acid (8.5 mol% based on rosin) was added, the amount of pentaerythritol added was 11.7% by weight, and the other operations were performed in the same manner as in Example 1. As a result, a rosin resin was obtained.

The softening point of this resin was 118 ° C, the acid value was 15.8, and the Gardner color tone was 7 ⁺ .

Comparative Example 3 100 parts by weight of gum rosin was charged into the same reactor as described in Example 1, heated to 180 ° C. under a nitrogen atmosphere, and stirred and melted.

Then, without performing addition reaction of acrylic acid,
0.07 parts by weight of palladium carbon (5% Pd-C) was added, the temperature was raised to 280 ° C., and the asymmetric reaction was carried out until the conjugated dienoic acid became 0.5% or less.

Then, after melting the catalyst to remove the catalyst, 100 parts by weight of the asymmetric asymmetric rosin and 9.5 parts by weight of glycerin were charged into the reactor, and esterification was performed at 280 ° C. for 15 hours under a nitrogen stream to obtain a rosin-based resin. Got

The softening point of this resin was 98 ° C., the acid value was 7.5, and the Gardner color tone was 8.

Comparative Example 4 A rosin resin was obtained in the same manner as in Comparative Example 3 except that pentaerythritol was used instead of glycerin in the operation of Comparative Example 3.

The softening point of this resin was 105 ° C., the acid value was 15.4, and the Gardner color tone was 9.

Comparative Example 5 100 parts by weight of gum rosin was charged into the same reaction apparatus as described in Example 1, heated to 180 ° C. under a nitrogen atmosphere and stirred and melted. Then 3.5 parts by weight of acrylic acid (vs. rosin 16.
1 mol%) was added dropwise at the same temperature, the temperature was raised to 200 ° C., and the addition reaction of acrylic acid was carried out under reflux.

Then, without performing the asymmetric reaction on the product,
100 parts by weight of the product and 12.5 parts by weight of pentaerythritol were charged into the reactor, and esterification was carried out at 280 ° C. for 15 hours under a nitrogen stream to obtain a rosin resin.

The softening point of this resin was 113 ° C., the acid value was 16.0, and the Gardner color tone was 8.

Comparative Example 6 100 parts by weight of 25% polymerized rosin (Polypar resin made by Rika Hercules Co., Ltd.) was charged in the same reaction apparatus as in Example 1, and heated at 180 ° C. under a nitrogen atmosphere to melt with stirring.
Next, 9.9 parts by weight of pentaerythritol was added, and esterification was carried out at 280 ° C. for 15 hours in a nitrogen stream to obtain a rosin resin.

The softening point of this resin was 120 ° C., the acid value was 15.5, and the Gardner color tone was 7.5.

Preparation of Hot Melt Adhesive Composition Using the rosin-based resin obtained in each of Examples and Comparative Examples as a tackifying resin, a hot melt adhesive composition was prepared with the following formulation.

EVA (Mitsui DuPont Polychemica 40 parts by weight, product name Eva Flex # 220, vinyl acetate content 28%, MI250, manufactured by Le Co., Ltd.) Adhesive resin 40 parts by weight Paraffin wax (Nippon Seishaku Co., Ltd. 20 parts by weight formula company, melting point 156 ° F.) Test method The following performance test was performed on the hot melt adhesive composition using each rosin resin obtained in each of the above Examples and Comparative Examples.

The degree of turbidity when mixing sample compositions at 180 ° C is
It was visually observed.

○: Transparently compatible.

Δ: Slightly inferior heating stability 50 g of the sample composition was placed in a 100 cc beaker and left standing in a circulating hot air dryer at 160 ° C. for 100 hours to visually observe the degree of skinning and turbidity.

Skinning ◎: No skinning ○: Almost no skinning ×: Skinning on the surface XX: Thick skinning on the entire surface Muddy ◎: Transparent and no muddy △: Slightly muddy ×: Cloudy and transparent None Adhesive strength A composition in which each component was thoroughly mixed at 180 ° C was applied to a 25 mm x 13 mm area of a single birch tree (25 mm x 150 mm),
Other same plates were stuck together to obtain a test piece.

Attach the above test piece to the strograph tester and press at 5mm / min.
Shear adhesive strength was measured by pulling at a speed of.

Test results The results of each of the above tests are shown in the table.

Effects of the Invention According to the present invention, as is clear from the test results,
The hot melt adhesive composition is extremely excellent in heating stability, and even after 100 hours have passed in the heating and melting state, both haze and skinning are extremely good.

The one that uses raw camrosin as the raw material rosin,
A slight peeling is observed after 100 hours, but it is not seen at all by using the purified rosin.

The hot melt adhesive compositions described in the above publications can barely be used again in 50 hours, as shown in Comparative Examples 1 and 2, but after 100 hours, they are both skiny and in a bad muddy state. It was difficult to use.

Further, as shown in Comparative Examples 3 and 4, those to which acrylic acid is not added are excellent in heating stability, but have a low melting point, poor adhesive strength, and poor color tone.

In addition, for those that do not have asymmetric rosin,
As shown in Comparative Example 5, the heating stability is extremely poor.

Therefore, in the tackifying resin in the hot melt adhesive composition of the present invention, it can be understood that the three requirements of addition of acrylic acid to a rosin, asymmetry and esterification with a polyhydric alcohol are essential.

Claims (4)

(57) [Claims] 1. A hot melt adhesive composition comprising an ethylene-vinyl acetate copolymer, a wax and a tackifying resin as main components, wherein the tackifying resin is a disproportionated rosin partially added with acrylic acid. Hot melt adhesive composition characterized by being a polyhydric alcohol ester 2. The hot melt adhesive composition according to claim 1, wherein the rosin, which is a raw material of the tackifying resin, is purified. 3. The hot melt adhesive composition according to claim 1, wherein the addition ratio of acrylic acid to the raw material rosin in the tackifying resin is 2.3 to 45 mol%, and the tackifying resin has a softening point. Hot-melt adhesive composition characterized by being at 100 to 140 ° C. 4. An addition reaction of acrylic acid, an asymmetric reaction and an esterification reaction with a polyhydric alcohol are carried out on rosin, and the resulting rosin resin is mixed with an ethylene-vinyl acetate copolymer and a wax. A method for producing a hot melt adhesive composition, characterized by mixing