JP2839907B2 - Resin dispersion with excellent low-temperature heat sealability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin dispersion useful as a paint or an adhesive, and more particularly, to a resin dispersion having excellent low-temperature sheet sealing properties.

(Prior art and its problems) Modified polypropylene partially or entirely graft-modified with an unsaturated carboxylic acid or an anhydride thereof,
The modified polypropylene powder obtained by evaporating the resin composition dispersed in a hydrocarbon solvent in a solid state to dryness at room temperature has the following conditions: (a) the degree of crystallinity measured by X-ray diffraction method is 70% (B) the intrinsic viscosity [η] is in the range of 0.3 to 1.5 dl / g, and (c) the content of the unsaturated carboxylic acid or its anhydride is
It has been proposed by the present applicant that a resin dispersion satisfying the following condition: 0.1 to 10% by weight is useful as a paint or an adhesive (Japanese Patent Application Laid-Open No.
-12651).

The present inventors have pursued a resin dispersion having particularly excellent low-temperature heat-sealing properties in the process of re-testing the invention, and found that the crystallinity measured by the X-ray diffraction method under the condition (a) was reduced. By making the melting point measured by differential thermal analysis 120 ° C or more and 160 ° C or less,
The inventors have found that a resin dispersion satisfying the above conditions can be obtained, and have reached the present invention.

Therefore, an object of the present invention is to provide a resin dispersion which can be used as an adhesive for polyolefins having excellent low-temperature heat sealability.

(Means for Solving the Problems) That is, according to the present invention, a modified polypropylene partially or entirely graft-modified with an unsaturated carboxylic acid or an anhydride thereof is dispersed in an organic solvent in a solid state. In the resin dispersion, the modified polypropylene powder obtained by evaporating the dispersion to dryness at room temperature is represented by the following (a)
(D) a resin dispersion having excellent low-temperature heat-sealing properties, characterized by having the properties of (d): (a) a melting point of 120 ° C. or more and 160 ° C. measured by differential thermal analysis
The following (b) Crystallinity measured by X-ray diffraction method is 50% or more
(C) intrinsic viscosity [η] of 0.3 to 1.5 dl / g (d) unsaturated carboxylic acid or anhydride content
0.1 to 10% by weight is provided.

Furthermore, according to the present invention, the polypropylene is a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and the propylene component in the copolymer is 90 mol% or more and 99 mol% or less. And when the organic solvent is a mixed solvent of a hydrocarbon solvent which is a parent solvent for the polymer and a polar solvent which is a poor solvent for the polymer, a more excellent low-temperature heat-sealing resin dispersion can be obtained. Can be

(Preferred Embodiment of the Invention) Modified Polypropylene The modified polypropylene used in the present invention is obtained by partially or entirely grafting an unsaturated carboxylic acid or an anhydride thereof to polypropylene. The raw material polypropylene is propylene and other α-olefins such as ethylene, 1-butene, isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, Methyl-1-pentene, 2-
1 to 10 of methyl-1-pentene, 1-heptene, etc.
Mol% random copolymer, and these polypropylenes have a melting point of 120 to 160 as measured by differential thermal analysis.
The first requirement is to be in the range of ° C. If the raw material polypropylene is a propylene homopolymer, the melting point will be 160 ° C or higher, and when used as a heat sealing material, the sealing temperature will rise to 170 ° C or higher, causing adverse effects such as warpage on the adherend. give.

Conversely, the copolymer component becomes 10 mol% or more, and the melting point of polypropylene becomes 120 ° C. or less, so that it cannot withstand the heating temperature in the case of performing the retort treatment.

As the unsaturated carboxylic acid or its anhydride to be grafted, acrylic acid, unsaturated monocarboxylic acid such as methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, allyl succinic acid, mesaconic acid, glutaconic acid, nadic Unsaturated dicarboxylic acids such as acid, methylnadic acid, tetrahydrophthalic acid and methylhexahydrophthalic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic anhydride, glutaconic anhydride, nadic anhydride, methylnadic anhydride Examples thereof include unsaturated dicarboxylic anhydrides such as acid, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. A mixture of two or more of these components may be grafted simultaneously. Among these unsaturated carboxylic acids or acid anhydrides thereof, it is preferable to use maleic acid, maleic anhydride, nadic acid or nadic anhydride.

A well-known method can be adopted as the grafting method. For example, the reaction is carried out by heating the polypropylene and the unsaturated carboxylic acid to a high temperature in the presence or absence of a solvent, with or without the addition of a radical initiator.

The second requirement of the modified polypropylene powder in the present invention is that the crystallinity measured by the X-ray diffraction method is 50%.
As mentioned above, it must be less than 70%.

This is because when the resin dispersion of the present invention is evaporated to dryness at room temperature, a particle powder of modified polypropylene is obtained. The powder is measured by an X-ray diffraction method as it is without applying heat. It means that the obtained crystallinity is 50% or more and less than 70%, and it is preferable that the crystallinity be in the range of 50 to 60%.

If the degree of crystallinity exceeds 70%, the heat seal strength at low temperature is not sufficient, and if it is less than 50%, the heat resistance of the seal part decreases, and the yield of polypropylene as a raw material becomes extremely low. It lacks industrial practicality. Further, those having a crystallinity within the above range, the particles easily swell in the organic solvent, by controlling the storage temperature to 20 to 30 ℃, it is possible to prevent aggregation, at this time, poor solvent for the resin By adding
More stable storage can be achieved.

As the poor solvent, alcohols, ketones, ethers, acid anhydrides, esters, cellosolves, etc. are used. Specifically, methanol, ethanol, propanol, butanol, pentanol, hexanol, propanediol, phenol , Water, diethyl ether, dipropyl ether, dibutyl ether, anisole, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, methyl isobutyl ketone, bentanone, hexanone, isophorone, acetophenone, acetic anhydride, methyl acetate, ethyl acetate, butyl acetate, methyl propionate ,
Examples include butyl formate, ethyl cellosolve, and methyl cellosolve.

The modified polypropylene powder of the present invention further has a grafting amount of an unsaturated carboxylic acid or the like in the range of 0.1 to 10% by weight, preferably 0.3 to 3% by weight, and an intrinsic viscosity [η] in decalin at 135 ° C of 0.3 to 0.3%. Or 1.5dl
/ g, preferably in the range of 0.5 to 1.2 dl / g.

The graft amount of the unsaturated carboxylic acid or its anhydride is 0.
Less than 1% by weight results in poor adhesion to metals, while more than 10% by weight results in poor adhesion to polyolefins. When the intrinsic viscosity [η] is less than 0.3, the modified polypropylene has insufficient cohesive strength and lacks adhesive strength, whereas when the intrinsic viscosity exceeds 1.5 dl / g, it lacks the fluidity of dissolving properties. Or it becomes difficult to obtain an adhesive layer.

Resin Dispersion The resin dispersion of the present invention is obtained by dispersing the modified polypropylene in an organic solvent in a solid state.

As the organic solvent, those which can dissolve the modified polypropylene at high temperature and do not substantially dissolve at room temperature, for example, aromatic hydrocarbons such as toluene and xylene, cyclohexane, alicyclic hydrocarbons such as methylcyclohexane, Examples thereof include aliphatic hydrocarbons such as hexane, heptane, decane, and mineral spirits.

However, in the dispersion obtained using these organic solvents, the dispersed particles may be redissolved by heating during storage, and may cause agglomeration when cooled again. Therefore,
In order to prevent such aggregation, it is preferable to add a poor solvent for the polymer described above.

In the resin dispersion of the present invention, pigments, fillers, stabilizers and other compounding agents known per se can be arbitrarily compounded as long as the object of the present invention is not impaired.

[Method for Producing Resin Dispersion] In order to produce the resin dispersion of the present invention, the above-mentioned modified polypropylene is mixed with a hydrocarbon-based solvent so that the concentration of the solids in the dispersion usually falls within the above range, Dissolve completely by heating. The temperature at the time of dissolution is usually 120 to 150 ° C. The solution is then cooled to precipitate the modified polypropylene, but it is necessary to adjust the average cooling rate in the temperature range from 70 to 90 ° C. to 1 to 20 ° C./hour, preferably 3 to 10 ° C./hour. In this case, cooling is usually performed while stirring, and it is preferable that the cooling rate in the same temperature range is uniform. If the time is lower than the lower limit, it is not preferable in terms of production efficiency. The temperature range in which the cooling rate needs to be controlled is 90 to 70 ° C., but 150 to 90 ° C. and 70 to 30 ° C.
It is preferable to control the temperature in the same manner.

[Effect of the Invention] The resin dispersion of the present invention hardly agglomerates since the dispersed particles hardly swell and dissolve, and even if the particles settle by standing, they can be easily and uniformly dispersed by lightly stirring. You can make things. Therefore, even when used as a paint, a coating material or an adhesive, the occurrence of troubles such as clogging of a nozzle of a coating machine can be suppressed, and almost no irregularities are formed on the coating surface.

In addition, the resin dispersion of the present invention is used as a metal-to-metal, polyolefin-to-metal, or metal-to-polyolefin adhesive or heat sealant, in order to exhibit excellent adhesive strength, particularly to a polyolefin sheet having a concave portion for tablet storage. Not only is it excellent as an adhesive for tablet packaging containers that heat-seal by covering its upper surface with metal foil,
It is also effectively used as a paint with excellent coating properties.

(Examples) Hereinafter, the present invention will be described in detail based on examples.

Example 1 An ethylene-propylene random copolymer containing 4.3 mol% of ethylene, having an X-ray crystallinity of 61%, and a melting point of 140 ° C. as measured by differential thermal analysis was adjusted to a concentration of 250 g / toluene in toluene. And heated to 140 ° C. in an autoclave, stirred and dissolved.

To 100 parts by weight of this polypropylene solution, 3.3 parts by weight of maleic anhydride and 0.9 parts by weight of dicumyl peroxide were added at 140 ° C. over 4 hours. After completion of the addition, stirring was continued for 1 hour, and then the mixture was cooled. After cooling, acetone was added to the solution to precipitate a polymer, and the precipitated polymer was separated by filtration, washed with a sufficient amount of acetone, filtered and dried to obtain a modified polypropylene.

[Η] of this modified polypropylene was 1.1 dl / g, and the maleic anhydride content was 0.8% by weight.

Next, 15 parts by weight of the modified polypropylene and toluene
85 parts by weight were placed in an autoclave equipped with a stirrer, heated to 140 ° C to completely dissolve the resin, and then stirred at 25 ° C /
After the temperature was lowered to 90 ° C. at a time cooling rate, it was gradually cooled to 70 ° C. at a cooling rate of 5 ° C./hour. Subsequently, when the temperature was lowered to 30 ° C. at a cooling rate of 40 ° C./hour, a milky white uniform dispersion was obtained.

The average particle size of the dispersed particles of the dispersion was 7 μ as measured by a Coulter counter.

The dispersion was filtered through a 100-mesh SUS screen filter, and the residue was dried and weighed. The residue was 0.1 parts by weight or less based on 100 parts by weight of the dispersion.

The polymer powder obtained after drying the dispersion under reduced pressure at room temperature for 24 hours was filled in a glass holder, and the crystallinity was measured by an X-ray diffraction method to be 58%.

Apply the dispersion to aluminum foil using a percoder
After air-drying, set in air open at 200 ° C.
Upon heating for 0 seconds, a coated foil having a uniform and transparent coating was obtained. That is, the film appearance was uniform. This coated foil and PP sheet (TOCELLO CHEMICAL # 500T-T) are JIS Z1
After applying a pressure of ² kg / cm ² at 180 ° C. for 2 seconds and applying a pressure of ² kg / cm ² by a method based on 707, the peel strength at normal temperature (18
(0 degree peeling) was 3.5 kg / 15 mm.

Similarly, the peel strength at room temperature when the heat bonding temperature was 160 ° C. was 2.0 kg / 15 mm.

In addition, the peeled surface showed good appearance without sticking on both the foil side and the PP side.

When the dispersion was taken in a stoppered measuring cylinder and allowed to stand at room temperature for 3 months, the dispersed particles had completely settled.
The cylinder was shaken by hand for 1 minute to recover a uniform dispersion. The recovered dispersion was filtered through a 100-mesh filter, and the remaining amount of filtration was measured.
It was 0.1 part by weight or less based on part by weight, and it was confirmed that redispersibility was good.

Examples 2 to 6 and Comparative Example 1 Dispersions were prepared by changing various conditions in Example 1, and the performance was examined in the same manner as in Example 1.

 Table 1 shows the conditions and results.

Continuation of front page (72) Inventor Akio Morinaga 6-1, 1-2 Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (56) References JP-A-59-217709 (JP, A) 1988-12651 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08F 255/00-255/10 C08L 51/06 C09D 151/06 C09J 151/06

Claims (3)

(57) [Claims] 1. A resin dispersion in which a modified polypropylene partially or entirely graft-modified with an unsaturated carboxylic acid or an anhydride thereof is dispersed in an organic solvent in a solid state, and the dispersion is evaporated to dryness at room temperature. A resin dispersion having excellent low-temperature heat sealability, wherein the modified polypropylene powder obtained by solidification has the following properties (a) to (d). (A) 160 ° C when the melting point measured by differential thermal analysis is 120 ° C or more
The following (b) Crystallinity measured by X-ray diffraction method is 50% or more
(C) intrinsic viscosity [η] of 0.3 to 1.5 dl / g (d) unsaturated carboxylic acid or anhydride content
0.1 to 10% by weight 2. The polypropylene according to claim 1, wherein the polypropylene is a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, and the propylene component in the copolymer is 90 to 99 mol%. Item (1). 3. The resin dispersion according to claim 1, wherein the organic solvent is a mixed solvent of a hydrocarbon solvent which is a parent solvent for the polymer and a polar solvent which is a poor solvent for the polymer.