KR100805790B1 - Hot melt adhesive - Google Patents

Abstract

A hot melt adhesive is provided to increase initial adhesion and to improve physical properties as compared with a solvent type adhesive while maintaining holding force and adhesion. A hot melt adhesive comprises: a blend of liquid resin with liquid rubber; and an adhesion enhancer containing a prepolymer of diisocyanate with polyol, wherein the liquid rubber is styrene isoprene styrene rubber whose diblock content is at least 75 wt%. The prepolymer has a ratio of NCO in diisocyanate to OH in polyol, i.e. [NCO]/[OH] ratio of 2-3 with residual NCO functional groups. The polyol has a number average molecular weight of 4,000-8,000.

Description

Hot Melt Adhesive

The present invention relates to a hot melt adhesive used in a BOPP (Bi-axially Oriented PolyPropylene) tape and the like, and more particularly to a hot melt adhesive with improved initial adhesive strength and appearance.

The adhesive tape can be divided into a solvent type and a hot melt adhesive tape.

Solvent-type tapes are prepared by mixing a raw material of adhesive and an organic solvent to liquefy, apply it on a tape, and then dry in a duct to volatilize the solvent and then wind it up. In the case of the solvent type, there is no bubble in the pressure-sensitive adhesive, but it takes a long time to volatilize and dry the organic solvent, so that the winding is slowed down to about 30 m per minute, thereby decreasing productivity.

In other words, in the case of the organic solvent-type adhesive, bubbles should not be generated. However, due to environmental problems, developed countries have restricted its use, and it takes a long time to make a tape product because it takes time to dry after applying to a tape. There is this.

Hot melt tape is produced by dissolving a pressure-sensitive adhesive is applied to the tape and then cured. The winding speed is 200 m per minute, and the productivity is high. However, the surface is uneven due to bubbles generated during application and winding.

The hot melt adhesive has no problem of environmental pollution, but first, bubbles are generated when the film is applied and wound to produce a tape, and second, the initial adhesive strength is bad, and aging occurs.

The hot melt method itself is more environmentally friendly because it does not use organic solvents, but in Korea, its physical properties are worse than solvent type and are not distributed. Most problematic is that the initial adhesive strength is weak compared to the organic solvent-type adhesive. This does not work in the domestic market where there is a lot of manual work, and aging is also a problem because there are four seasons.

In the case of the hot melt process, the working environment of the workers is of course unclean. However, when the hot melt method is used, since the initial adhesive strength is too much lower than the solvent type, workability is poor during manual work. Therefore, it was not available in Korea. However, the tape using the solvent-type adhesive in the process of the rapid spread of the Chinese tape recently can not afford the price. An alternative is the hot melt adhesive tape, which has a tremendous advantage over solvent type productivity. However, as mentioned above, there are two problems, namely, the physical properties of the product are inferior, and the second, the appearance is bad.

An object of the present invention is to provide a hot-melt pressure-sensitive adhesive exhibiting better physical properties than a solvent-type pressure-sensitive adhesive by increasing the initial adhesive strength without dropping the holding and adhesive strength of the existing hot melt pressure-sensitive adhesive.

Another object of the present invention is to provide a hot melt pressure-sensitive adhesive that improves the bad appearance due to severe bubble marks.

In order to achieve the above object, the present invention provides a hot melt pressure-sensitive adhesive comprising a pressure-sensitive adhesive (hereinafter referred to as DI-100) containing a mixture of a liquid resin and a liquid rubber and a prepolymer of a diisocyanate and a polyol.

In order to apply the moisture-curable principle in the present invention, it is preferable to use a prepolymer having NCO functional groups remaining as [NCO] / [OH], which is the OH ratio of the NCO of the diisocyanate and the polyol, of 2 to 3.

In the present invention, the content of the NCO functional group is preferably 3 to 8% by weight in consideration of CO ₂ generation and crosslinking (curing) power caused by moisture.

In the present invention, the number average molecular weight of the polyol is preferably 4,000 to 8,000 so as to increase the molecular weight of the prepolymer to exert the strong initial adhesive strength of the hot melt adhesive.

In the present invention, as the liquid rubber, SIS rubber (Styrene Isoprene Styrene Rubber) is preferable, and in particular, SIS rubber having a diblock content (Diblock Content) of 75 wt% or more is preferable. Block means a branched chain in the block copolymer, the higher the diblock content, the softer the copolymer, which is advantageous for improving the initial adhesive force.

In the present invention, as the liquid resin, rosin ester (liquid rosin) having a very low softening point (existing in a liquid state at room temperature) and low cost is preferable.

The hot melt adhesive according to the present invention includes a thermoplastic elastomer (TPE), a petroleum resin, a softener, a tackifier, an anti-aging agent, etc. in addition to DI-100.

In the present invention, the thermoplastic elastomer (TPE) is preferably a styrene (Styrene Isoprene Styrene) block copolymer in consideration of compatibility with DI-100. If the styrene or diblock content of this SIS changes, the rubber: resin ratio or oil content can be adjusted accordingly.

In the present invention, the petroleum resin is preferably a C5 to C9 (C5-C9) aliphatic petroleum resin to which aromatics are added in consideration of compatibility with a highly polar elastomer.

In the present invention, the softener is preferably a paraffinic oil in consideration of polarity and viscosity suitable for workability.

In the present invention, the tackifier is preferably polybutene to improve moisture resistance and processability.

The present invention is characterized by minimizing the generation of bubbles by increasing the flowability (increased fluidity) to the hot melt adhesive, for this purpose it is characterized by using a rubber with a high diblock content, liquid resin and moisture-curable hot melt adhesive principle.

DI-100 used in the present invention is a small amount but plays a key role. First, the polyol and diisocyanate are reacted in bulk in a similar manner to the process of preparing a moisture-curable reactive hot melt adhesive, and the ratio of the two reactants is between 2 and 3, so that some NCO functional groups remain. To form a high molecular weight prepolymer. At this time, the NCO functional group content is 2 to 10 wt%. This was determined after sufficient testing in consideration of CO ₂ generation and crosslinking (curing) power caused by moisture.

In addition, the polyol to be used has a number average molecular weight of 4,000 to 8,000, such as a polyester type polyol to increase the molecular weight of the prepolymer to exhibit a strong initial adhesive strength of the hot melt pressure-sensitive adhesive. Moisture-curable polyurethanes first convert some NCO groups to amine (NH ₂ ) groups by moisture when the PU molecules with NCO groups are melted by heat, exposed to air and applied to the adherend. And the amine group reacts continuously with the NCO group which did not bind with water.

In other words, the prepolymer NCO group, which is the principle of moisture curing, reacts with the water of the bubble to be aminated and the amine group reacts with the unreacted NCO of other molecular chains to form urea bonds. The functional groups move together with liquid resins with extremely good wetting properties and SIS rubbers with high diblock content, allowing other NCO groups to continuously crosslink and cause organosilanes that are bound to the molecular chain. The majority of electrons react to form new crosslinks while hydrolyzing with water. This is because the area occupied by the bubbles is smaller than the total area.

Unlike the general moisture-curable reactive hot melt adhesive in the present invention, because it is mixed with the pressure-sensitive adhesive and applied to the film and the film is laminated on it again, a liquid resin having good fluidity must be put in the NCO group which does not react with bubbles and crosslinks with the amine. Can be.

In addition, in the present invention, it is possible to increase the initial adhesive strength and adhesion by putting a SIS rubber and a liquid resin having a high diblock content in order to exhibit superior physical properties than the solvent type.

The SIS rubber and liquid resin having a high diblock content not only have physical properties but also improve the flowability of the hot melt pressure-sensitive adhesive raw material, thereby playing a role of no bubble generation. Therefore, when this moisture hardening is performed, the aging phenomenon of the adhesive hardly occurs.

The experimental standard of aging is almost unchanged when the physical property is tested after being left at 70 ° C. for 3 days, and aging is very severe in the case of a conventional solvent type or other hot melt adhesive.

The raw material of the hot melt adhesive according to the present invention is as follows.

1.Thermoplastic Elastomer

SIS (Styrene Isoprene Styrene) Block Copolymer is used as the base polymer.

2. Petroleum Resin

The addition of aromatic aliphatic (C5-C9) petroleum resins results in excellent compatibility with various elastomers, especially relatively polar elastomers such as SIS.

3. Softeners

It is used as a lubricant between rubber molecules for the purpose of mixing with pressure-sensitive adhesives to improve flexibility, processability, etc., and paraffinic process oil is used in consideration of polarity and viscosity suitable for workability.

4. Tackifier

The second petroleum resin is also included as a raw material to increase adhesion, but in addition to the petroleum resin, polybutene is used to improve moisture resistance and processability.

5. Age Resister

It is added to prevent the adhesive from oxidizing.

6. DI-100

As a core raw material of the present invention, the liquid petroleum resin & diblock high content of SIS rubber, diisocyanate and polyol reactants, antioxidants and the like.

DI-100 is 30 to 70% by weight of a mixture of liquid resin & liquid rubber, 30 to 70% by weight of diisocyanate and polyol reactant, 0 to 5% by weight of antioxidant, preferably high liquid rosin & diblock SIS rubber 40 To 60% by weight, 40 to 60% by weight of diisocyanate and polyol reactant, and 0 to 1% by weight of antioxidant.

DI-100 allows the bubbles of hot melt tape to be removed within two to three days (correction) of tape production. This is a method in which the bubbles in the tape are cured at room temperature with diisocyanate and spread out to remove bubbles.

Method for producing a hot melt adhesive according to the present invention is as follows.

Normally, the temperature of 160 to 170 ℃ to give a stirrer and the first petroleum resin and paraffin oil while operating the impeller to stir and melt and when the polybutene, antioxidant and rubber is added, the rubber is usually added three times. When petroleum resin and rubber are added at the same time, stirring is not good, so they are added sequentially without adding them simultaneously.

Finally add DI-100 raw material and stir for 30 minutes. The total stirring time is about 2 hours 30 minutes. When using the pressure-sensitive adhesive is applied to the film after dropping to about 110 ℃ from the initial temperature. This is due to the heat resistance of the film.

EXAMPLE

The stirrer was given a temperature of 165 ℃ and the petroleum resin and paraffin oil were added first, and the impeller was operated to stir, and when it melted, polybutene, antioxidant, and rubber were added three times. Finally, DI-100 raw material was added and stirred for 30 minutes. The total stirring time was about 2 hours 30 minutes. After dropping to about 110 ℃ from the initial temperature was applied to the OPP film to prepare a hot melt adhesive OPP tape.

At this time, the hot melt adhesive was prepared as shown in Table 1, DI-100 raw material was prepared as shown in Table 2.

ingredient content SIS Rubber C5 Petroleum Resin C5 / C9 (Copolymerization) Petroleum Resin Softener (Paraffin Oil) Tackifier (Polybutene) Antioxidant (Iganox 1010) DI-100 50 kg 40 kg 10 kg 9 kg 6 kg 0.5 kg 10 kg

ingredient content Liquid Rosin & SIS Rubber (78% Diblock, 15% Styrene) Diisocyanate and Polyol Reactant ([NCO] / [OH] = 2.5) Antioxidant 49.5 wt% 50 wt% 0.5 wt%

[Test Example]

The adhesive performance of the hot melt adhesive tape prepared in Example and the conventional products was measured and the results are shown in Table 3. The adhesion performance test method was tested according to JIS-Z0237 standard.

1. Peel Strength Test (180 °, 90 °)

The stainless steel (sus) plate was washed clean with toluene solvent. A test piece (tape) was attached to the sus plate at an angle of 180 degrees, and reciprocally crimped twice with a 2 kg rubber roller. Twenty to thirty minutes after compression, the test equipment was used for testing. Peeling rate was 300 mm / min. The width of the test piece was 25 mm and the sus plate attachment area was 25 mm x 100 to 150 mm.

2. Initial Tack Test

The Rolling Ball Tack rolled the ball on a 30-degree inclined test plate and chose the length (cm) to stop at the adhesive surface.

3. Cohesion test

A test piece having a width of 25 mm and a length of 130 mm was produced, and one side of the test piece was attached to the sus plate so as to have an area of 25 × 25 mm, and pressed with a roller. The weight of 1 kg load was hung on the end of the test piece, and the time to drop further was made into holding force.

OPP Tape Cloth tape Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Example Comparative Example 4 Rolling Ball Tack (cm) Early 3.2 0.5 1.3 0.0 12 0.0 Weather 3.9 12.1 4.6 7.4 1.6 0 J.Dow Ball Tack (Ball Number) Early - - - - - - Weather - - - - - - Loop Tack (kgf) Early 2.44 3.25 1.72 1.37 3.28 2.14 Weather 1.87 0.67 1.17 0.97 3.54 1.66 Peel Strength (㎏f / in) Early 2.38 1.95 1.3 0.58 7.0 or higher 2.7 Weather 1.57 0.75 1.03 0.37 7.0 or higher 1.68 Cohesion (50 ℃) (min) Early 457 1410 ＞ 8000 146 11 4 Weather 537 468 ＞ 8000 178 31 7 * Example: Hot Melt, Comparative Example 1: Hot Melt (domestic), Comparative Example 2: Hot Melt (foreign), Comparative Example 3: Solvent (domestic), Comparative Example 4: NR Base (domestic) * Weathering conditions: 70 ℃ × 72hrs

EXAMPLE The initial rolling force of the tape (Rolling Ball Tack) is inferior to other samples at first, but the weather resistance is very good so that it shows the best after weathering (ie oxidation).

EXAMPLES The adhesive force of the tape is much better from the beginning, and its value drops the least even after the weathering.

Example The cohesive force (holding force) of the tape is initially lower than that of domestic hot melt, but is better after oxidation, and is superior to the solvent-type adhesive from the beginning.

According to the present invention, the initial adhesive strength can be increased without lowering the holding force and adhesive strength, which are advantages of the conventional hot melt adhesive, and can exhibit better physical properties than the solvent-type adhesive, and also have a bad appearance due to the severe bubble marks, which is a disadvantage of the conventional hot melt adhesive. It can be improved.

Claims (12)

Adhesion improving agent containing a mixture of liquid resin and liquid rubber and prepolymer of diisocyanate and polyol, Liquid rubber is SIS rubber (Styrene Isoprene Styrene Rubber), A hot melt pressure sensitive adhesive, characterized in that the diblock content of the SIS rubber is 75% by weight or more. The hot melt pressure-sensitive adhesive according to claim 1, wherein [NCO] / [OH], which is the OH ratio of the NCO of the diisocyanate and the polyol, is a prepolymer having 2 to 3 NCO functional groups remaining. The hot melt pressure-sensitive adhesive according to claim 2, wherein the content of the NCO functional group is 3 to 8% by weight. The hot melt pressure sensitive adhesive according to claim 1, wherein the polyol has a number average molecular weight of 4,000 to 8,000. delete delete The hot melt pressure sensitive adhesive according to claim 1, wherein the liquid resin is rosin ester (liquid rosin). The hot melt pressure-sensitive adhesive according to claim 1, further comprising polybutene and an antioxidant as a thermoplastic elastomer (TPE), a petroleum resin, a softener, and a tackifier. The hot melt adhesive according to claim 8, wherein the thermoplastic elastomer (TPE) is a SIS (Styrene Isoprene Styrene) block copolymer. The hot melt pressure-sensitive adhesive according to claim 8, wherein the petroleum resin is a C5 to C9 (C5-C9) aliphatic petroleum resin to which aromatics are added. The hot melt pressure-sensitive adhesive according to claim 8, wherein the softener is paraffinic oil. delete