JPH10130436A - Hot-melt composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hot-melt compsn. greatly improved in heat resistance of adhesion and having good low-temp. adhesiveness and workablity by combining an ethylene-vinyl acetate copolymer with another ethylene-vinyl acetate copolymer different in melt index and vinyl acetate content from the former copolymer. SOLUTION: The first ethylene-vinyl acetate copolymer(EVA) has a melt index(MI) of 10-5,000g/10min and a vinyl acetate content(VA) of 5-40wt.%. The second EVA has a MI of 10-800g/10min, a VA of 21-50wt.% a ratio (Mw/Mn) of wt. average mol.wt. (Mw) to number average mol.wt. (Mn) of 2.0-4.0, a content of low-mol.-wt. components (in terms of polystyrene, 15,000 or lower) of 24wt.% or lower, and an m.p.(MP) satisfying the relation: MP>=120-4.1[log(MI)]-1.33VA. The compounding ratio of the first copolymer to the second is (5:95)-(60:40).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt composition, and more particularly to a hot-melt composition containing an ethylene-vinyl acetate copolymer as a main component and having good heat resistance, cold resistance and workability. .

[0002]

2. Description of the Related Art A hot-melt adhesive is solvent-free, has a fast bonding speed, adheres to a relatively wide range of adherends, and can achieve automation and labor-saving of the bonding process.
For convenience, it has been used in place of conventional solvent-based adhesives and emulsion-based adhesives, and the amount of use has been increasing year by year. This hot melt adhesive is generally produced by mixing a thermoplastic resin as a main component, a tackifier and a wax as needed, and then melt-mixing them.

[0003] Examples of the thermoplastic resin used as a main component in the hot melt adhesive include polyolefin-based, polyamide-based, polyester-based, and synthetic rubber-based resins. Among them, polyolefins, especially ethylene-vinyl acetate copolymer, by changing the type and other components, high and low melt viscosity,
Because it is possible to freely prepare those with fast or slow solidification rate, it is possible to manufacture products that match each application, and it is also cheaper than other hot melt thermoplastic resins in terms of price, It is used in large quantities for a wide range of applications, such as packaging, bookbinding, and woodworking.

[0004]

However, the ethylene-vinyl acetate copolymer hot melt adhesive has a drawback that its heat resistance is low. For example, when articles bonded in summer are stored in a warehouse, the temperature in the warehouse becomes high, which may cause a problem that the adhesive is peeled off due to softening of the adhesive or the like. In order to improve the heat-resistant adhesiveness in order to solve this drawback, there has been a problem that the cold-resistant adhesiveness is deteriorated and the melt viscosity is increased to deteriorate the workability.

An object of the present invention is to provide an ethylene-vinyl acetate copolymer-based hot melt adhesive which is improved in heat-resistant adhesiveness in order to solve the above-mentioned troubles, and is also excellent in cold-resistant adhesiveness and workability. And

[0006]

Means for Solving the Problems The present inventors have made intensive studies to obtain an ethylene-vinyl acetate copolymer-based hot melt adhesive having both heat resistance, cold resistance and workability. As a result, reducing the low melting point component in the ethylene-vinyl acetate copolymer, that is, narrowing the molecular weight distribution, reducing the low molecular weight component, and reducing the ethylene-vinyl acetate copolymer
By increasing the melting point of the vinyl acetate copolymer,
It has been found that heat resistance can be improved. Furthermore, by combining this ethylene-vinyl acetate copolymer with another ethylene-vinyl acetate copolymer having a different melt index and vinyl acetate content, the cold adhesion resistance and workability are improved. Heading, the present invention has been completed.

That is, the present invention provides the following two kinds of ethylene-vinyl acetate copolymers (I) and (II): (I) a melt index of 10 to 5000 g / 10
-Vinyl acetate copolymer having a vinyl acetate content of 5 to 40% by weight, (II) Melt index 1
0-800 g / 10 min, vinyl acetate content 21-50
Weight%, weight average molecular weight (Mw) and number average molecular weight (M
n) and the content (Mw / Mn) of 2.0 to 4.0, and the content of low molecular weight components of 15,000 or less in terms of polystyrene is 24.
% By weight, melting point (MP), melt index (M
I) and the content of vinyl acetate (VA) are as follows: MP ≧ 120−4.1 [log (MI)] − 1.33 VA (where MP is in ° C. and MI is in g / 10 min.) , V
The unit of A is% by weight).
An object of the present invention is to provide a hot melt composition containing a vinyl acetate copolymer. The present invention also provides a hot melt composition obtained by adding up to 200 parts by weight of a tackifier and / or up to 150 parts by weight of wax to 100 parts by weight of the hot melt composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Among the ethylene-vinyl acetate copolymers (hereinafter abbreviated as "EVA") used in the present invention, EVA (I) has the following physical properties. -Melt index is 10 to 5000 g / 10 min.-Vinyl acetate content is 5 to 40% by weight.

The EVA of (II) has the following physical properties: Melt index: 10 to 800 g / 10 minutes Vinyl acetate content: 21 to 50% by weight Weight average molecular weight (Mw) and number average Ratio to molecular weight (Mn) (hereinafter abbreviated as “Mw / Mn ratio”) 2.0
4.0 Content of low molecular weight component of 15,000 or less in terms of polystyrene (hereinafter abbreviated as “low molecular component content”) 2
4% by weight or less Melting point (MP), melt index (MI), and vinyl acetate content (VA) satisfy the following relational expression (hereinafter, referred to as:
This formula is referred to as “melting characteristic formula”). MP ≧ 120−4.1 [log (MI)] − 1.33 VA (where MP is in ° C., MI is in g / 10 min, V
A unit is% by weight

The physical properties required for the above-mentioned EVA can be obtained by the following methods. [Melt index] Measured under the conditions of a temperature of 190 ° C and a load of 2160 g in accordance with JIS K7210.
When the MI is 100 g / 10 min or more, the measurement under the above measurement conditions (temperature 190 ° C., load 2160 g) is difficult.
IS K7210, the value (M
I ′), the following equation: log (MI) = 0.87 [log (MI ′)] + 1.8 (wherein the units of MI and MI ′ are g / 10
) And converted to a value (MI) measured under the measurement conditions of a temperature of 190 ° C and a load of 2160 g.

[Vinyl acetate content] JIS K673
It is measured according to 0.

[Mw / Mn ratio] The ratio is obtained from the weight average molecular weight (Mw) and number average molecular weight (Mn) measured by size exclusion chromatography.

[Low molecular component content] It is measured as a component having a molecular weight smaller than that of polystyrene having a molecular weight of 15,000 by size exclusion chromatography. .

[Melting point] Measured by a differential scanning calorimeter.

Whether the EVA of (II) satisfies the melting point characteristic equation is determined by the melting point (M
P), the melt index (MI), and the value of the vinyl acetate content (VA) are substituted into the melting point characteristic formula, and are determined by calculation.

In the EVA of (II), the Mw / Mn ratio is a value that serves as an index of the molecular weight distribution. The smaller the ratio, the narrower the molecular weight distribution and the more uniform the molecular weight. If the number is less than 2.0, it is difficult to produce by the high-pressure method, and if it exceeds 4.0, the heat-resistant adhesiveness is poor, which is not preferable for the purpose of the present invention. Similarly, when the content of the low-molecular component exceeds 24% by weight, the heat-resistant adhesiveness is not improved, so that it is not preferable.

On the other hand, EVA satisfying the melting point characteristic equation
Has a higher melting point than ordinary EVA having the same MI and VA, and therefore, by blending it, the heat-resistant adhesiveness of the hot melt composition can be greatly improved.

The above-mentioned EVA used in the present invention can be produced by a method called a high-pressure radical polymerization method. In this method, for example, the monomers ethylene and vinyl acetate are pumped into a reactor using a high-pressure pump,
In this method, copolymerization is performed using a radical generating catalyst such as an organic peroxide in a reactor under high temperature and high pressure conditions, and then the copolymer and unreacted monomer are separated in a high pressure separator.

Of the two types of EVA used in the present invention,
EVA of (I) was produced under the production conditions of the conventional high-pressure radical polymerization method, while EVA of (II) was produced under the following production conditions.

That is, the production of EVA of (II) preferably uses a tubular reactor, and the ratio of the length to the diameter of the reactor is about 250: 1 to 12000: 1. Is preferred. In addition, the polymerization reaction pressure is a pressure measured at the reactor inlet, conventionally 150 ~ 230MP
a, but in the production of EVA of (II), 235
３００300 MPa is desirable, and 240８０280 MPa is more desirable. Conventionally, the polymerization reaction peak temperature is 280 to
Although it was 330 ° C., it is preferably 200 to 260 ° C., more preferably 220 to 250 ° C. in the production of (II) EVA.

Furthermore, in the conventional high-pressure radical polymerization method for obtaining EVA of (I), no chain transfer agent is used.
In the method (II) of polymerizing EVA, a chain transfer agent is used. Examples of the chain transfer agent include α-olefins, alcohols, ketones, and aldehydes.

Specific examples of α-olefins used as a chain transfer agent include propylene, butene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, octene-1, and decene-1. And the like. Specific examples of alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol, and octyl alcohol.

Further, specific examples of ketones used as a chain transfer agent include acetone, diethyl ketone, diamyl ketone, diisobutyl ketone, methyl ethyl ketone, methyl isopropyl ketone, ethyl butyl ketone,
Ethyl propyl ketone, diisoamyl ketone, and the like. Specific examples of aldehydes include formaldehyde, acetaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, n-caprolaldehyde, and n-capryl. Aldehyde and the like.

Of these chain transfer agents, preferred are alcohols, ketones and aldehydes.

In the EVA polymerization method (II), the amount of the chain transfer agent used is preferably from 0.2 to 10 mol%, more preferably from 0.5 to 5 mol%, based on the total amount of the raw materials supplied to the reactor. % Is more desirable.

Further, as the radical generating catalyst used in the method for polymerizing EVA of (II), conventional catalysts are used, and examples thereof include organic peroxides, azo compounds, oxygen and the like. Conventionally, the amount of the radical generating catalyst used was 55 ppm by weight or more with respect to the total amount of the raw materials supplied to the reactor, but in the method (II) of polymerizing EVA, 1 to 50 ppm by weight is desirable. 5
-30 ppm by weight is more desirable.

In the present invention, the amount of each EVA is as follows:
EVA of (I) is 5 to 60% by weight, and EVA of (II) is 9% by weight.
The content is preferably set to 5 to 40% by weight. (I) EVA
If the EVA is less than 5% by weight, the workability may be poor, and if the EVA of (II) is less than 40% by weight, the heat-resistant adhesiveness may be inferior.

The hot melt composition of the present invention can be prepared by combining both of the above-mentioned EVAs, but it is also possible to add a tackifier or a wax if necessary.

EVA is used as a tackifier to be compounded.
It is desirable that the composition has good compatibility with the hot melt composition and has properties such as imparting hot tackiness to the hot melt composition and improving workability at the time of application. Examples thereof include the following.

(1) Terpene resin (2) Rosins such as rosin, esterified rosin, hydrogenated rosin (3) Aliphatic petroleum resin (4) Aromatic petroleum resin (5) Aliphatic / aromatic copolymer Petroleum resin (6) chroman / indene resin

These tackifiers may be used alone or as a mixture of two or more. The mixing ratio of the tackifier is EVA ((I) EVA and (I)
200 parts by weight or less, preferably 50 to 150 parts by weight, per 100 parts by weight of (I) the total amount of EVA). If the amount exceeds 200 parts by weight, the strength after bonding is undesirably reduced.

The wax to be compounded is EV
A good compatibility with A, increase the fluidity of the hot melt composition at the time of heating and melting, improve the workability at the time of coating, in some cases, improve the performance such as improving the heat-resistant adhesion. Preferably, the following are exemplified.

(1) Paraffin wax (2) Microcrystalline wax (3) Fischer-Tropsch wax (4) Polyethylene wax (5) Modified wax (6) α-olefin wax

These waxes may be used alone or as a mixture of two or more. The mixing ratio of the wax is 150 parts by weight or less, preferably 10 to 100 parts by weight, based on 100 parts by weight of EVA. If the compounding ratio exceeds 150 parts by weight, the flexibility, cold resistance, impact resistance and the like of the hot melt composition deteriorate, which is not preferable.

Further, the hot melt composition of the present invention includes:
Furthermore, various additives such as antioxidants, fillers, lubricants, light stabilizers, ultraviolet absorbers, antistatic agents, processing aids, plasticizers, foaming agents, and pigments may be added as necessary. it can.

In order to prepare the hot melt composition according to the present invention, it is only necessary to heat, mix and stir the above-mentioned components in a container, or it may be used for ordinary melt mixing of polymers.
A roll, a Banbury mixer, a kneader, an extruder, or the like may be used, and this may be formed into a desired shape, for example, a pellet shape, a flake shape, a slab shape, or the like. The hot-melt composition thus obtained is applied to an adherend such as paper, cloth, leather, wood, various synthetic resins, metals, and stones by melt coating using a normal hot-melt applicator or the like. You.

[0037]

The reason why the hot melt composition of the present invention has excellent heat-resistant adhesiveness is that the molecular weight distribution of EVA used (II) is narrower than that of the conventional EVA and has a high melting point. Such EVA uses a higher reaction pressure than conventional polymerization conditions, a lower concentration of a radical generation catalyst for ethylene and vinyl acetate monomers, and uses alcohols, ketones or aldehydes as chain transfer agents,
It can be manufactured by increasing the amount of use.
In addition, by adding an appropriate amount of the conventional EVA of (I) having a different melt index and vinyl acetate content in addition to the EVA of the above (II), the workability was improved without impairing the cold resistance. Furthermore, a high-performance hot melt composition can be obtained by blending a tackifier and a wax as needed.

[0038]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, Production Examples and Test Examples, but the present invention is not limited to these Examples and the like.

Production Example 1 Preparation of EVA-A (conventional method): In ethylene, 7.2 mol% of another raw material, vinyl acetate, and 125 wt% of di-t-butyl peroxide as a radical generating catalyst
pm was added (no chain transfer agent was used). This mixture was pumped into a tubular reactor using a high-pressure pump, and ethylene and vinyl acetate were copolymerized under a polymerization condition of a reaction pressure of 170 MPa and a reaction peak temperature of 320 ° C. to obtain EVA-A.

The physical properties of the obtained EVA (vinyl acetate (V
A) From the content, melt index, Mw / Mn ratio, low molecular component content, melting point) and their values, the following formula (1), 120-4.1 [log (MI)] -1.33 VA (1) The calculated value obtained in step (1) is described in parentheses (the comparison between the actually measured melting point and the calculated value is also described). The result is as follows.

VA content: 15% by weight Melt index: 850 g / 10 min Mw / Mn ratio: 5.2 Low molecular component content: 31% by weight Melting point: 77 ° C. Calculated value: 88.0 (The melting point is lower. Low )

Production Example 2 Preparation of EVA-B: In ethylene, 9.7 mol% of vinyl acetate as another raw material, 2.0 mol% of diethyl ketone as a chain transfer agent, and 25 wt% of a radical generating catalyst were used. p
pm was added. This mixture was pumped into a tubular reactor using a high-pressure pump, and ethylene and vinyl acetate were copolymerized under the polymerization conditions of a reaction pressure of 240 MPa and a reaction peak temperature of 250 ° C. to obtain EVA-B. The physical properties of the obtained EVA-B and the calculated values of the formula (1) are as follows, and the obtained EVA-B belongs to the EVA of (II).

VA content: 27% by weight Melt index: 360 g / 10 minutes Mw / Mn ratio: 3.4 Low molecular component content: 22% by weight Melting point: 76 ° C. Calculated value: 73.6 (The melting point is lower. high )

Production Example 3 Preparation of EVA-C: 9.2 vinyl acetate in ethylene
A mixture obtained by adding 1.8 mol% of a chain transfer agent, 10 mol ppm of a radical generating catalyst and a reaction pressure of 25 mol%
EVA-C was prepared in the same manner as in Production Example 2 except that the reaction pressure was 5 MPa and the reaction peak temperature was 240 ° C. EV obtained
The physical property values of AC and the calculated values of the formula (1) are as follows, and the obtained EVA-C belongs to the EVA of (II).

VA content: 28 wt% Melt index: 150 g / 10 min Mw / Mn ratio: 3.7 Low molecular component content: 21 wt% Melting point: 75 ° C. Calculated: 73.8 (melting point is lower high )

Production Example 4 Preparation of EVA-D (conventional method): A mixture of ethylene and 10.0 mol% of vinyl acetate and 105 ppm by weight of a radical generating catalyst (without using a chain transfer agent). And EVA-D was prepared in the same manner as in Production Example 1, except that the reaction pressure was 180 MPa and the reaction peak temperature was 330 ° C. The physical property values of the obtained EVA-D and the calculated values of the formula (1) are as follows, and the obtained EVA-D belongs to the EVA of (I).

VA content: 27% by weight Melt index: 360 g / 10 minutes Mw / Mn ratio: 4.8 Low molecular component content: 29% by weight Melting point: 63 ° C. Calculated value: 73.6 (The melting point is lower. Low )

Production Example 5 Preparation of EVA-E (conventional method): In ethylene, 11.1 mol% of vinyl acetate and 55 wt.
Using a mixture to which pm has been added (without using a chain transfer agent),
EVA-E was prepared in the same manner as in Production Example 1, except that the reaction pressure was 230 MPa and the reaction peak temperature was 320 ° C.
The physical properties of the obtained EVA-E and the calculated values of the formula (1) are as follows, and the obtained EVA-E is the EVA of (I).
Belonged to

VA content: 28% by weight Melt index: 150 g / 10 minutes Mw / Mn ratio: 5.7 Low molecular component content: 27% by weight Melting point: 65 ° C. Calculated value: 73.8 (The melting point is lower. Low )

EXAMPLES Preparation of Hot Melt Compositions: Hot melt compositions of products 1 to 3 of the present invention and comparative products 1 to 3 were prepared according to the raw material compositions shown in Table 1 below. That is, first, 300m
lPut the wax in a stainless steel beaker,
And melt it. Next, EVA is gradually added to the beaker while the temperature is maintained at 180 ° C., and the mixture is dissolved with stirring to obtain a uniform dissolved state. Further, the tackifier was gradually added to the beaker while maintaining the temperature at 180 ° C., and dissolved with stirring to prepare a hot melt composition in a uniform dissolved state.

[Raw material composition]

[Table 1]

In Table 1, products 1 to 3 of the present invention are all compositions using EVA satisfying the requirements of the present invention, whereas comparative products 1 and 2 correspond to products 1 and 2 of the present invention. The composition in which the conventional EVA is combined, Comparative product 3 is a composition of only one type of EVA.

Test Example Performance Test of Hot Melt Composition: Each of the hot melt compositions obtained in the examples was evaluated for melt viscosity, heat creep resistance and low-temperature adhesion by the following evaluation methods.
The results are shown in Table 2.

[Evaluation Method] (1) Melt Viscosity The melt viscosity was measured according to the hot melt adhesive test method JAI-7. The measurement temperature is 180 ° C.

(2) Heat Creep Property The heat creep property was measured according to the hot melt adhesive test method JAI-7. A test piece prepared according to the procedure of JAI-7 was measured at a temperature of 50 ° C. under a load of 300 gf until the test piece was peeled off, and evaluated by the time (F ₅₀ ) at which half of the test pieces were peeled off.

(3) Low Temperature Adhesiveness Measured according to hot melt adhesive test method JAI-7. The test piece prepared according to the procedure of JAI-7 was allowed to stand at a temperature of −20 ° C. for 24 hours, and the peeled surface was observed after the test piece was peeled off. If the substrate has been broken, the test is accepted.

[0057]

[Table 2]

As is evident from the results in Table 2, the product of the present invention was superior to the comparative product in heat creep resistance and workability and cold resistance. On the other hand, Comparative Products 1 and 2 were inferior in heat-resistant creep properties, and Comparative Product 3 was high in melt viscosity and therefore inferior in workability.

[0059]

The hot melt composition of the present invention, as one EVA, has a narrower molecular weight distribution than conventional ones,
EVA having a low molecular weight component, a high melting point, and a significantly improved heat-resistant adhesiveness is used. Further, the other EVA having a different melt index and vinyl acetate content is used.
Is used. By combining the two different types of EVA in this way, the ethylene-vinyl acetate copolymer hot melt composition having significantly improved heat-resistant adhesiveness and good low-temperature adhesiveness and workability can be provided. is there. The hot melt composition of the present invention having such excellent properties can be advantageously used in a wide range of applications such as packaging, bookbinding, and woodworking. that's all

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09J 191/06 C09J 191/06 193/04 193/04 (C08L 23/08 91:06 93:04)

Claims (4)

[Claims] 1. The following two ethylene-vinyl acetate copolymers (I) and (II): (I) a melt index of 10 to 5000 g / 10
-Vinyl acetate copolymer having a vinyl acetate content of 5 to 40% by weight, (II) Melt index 1
0-800 g / 10 min, vinyl acetate content 21-50
Weight%, weight average molecular weight (Mw) and number average molecular weight (M
n) and the content (Mw / Mn) of 2.0 to 4.0, and the content of low molecular weight components of 15,000 or less in terms of polystyrene is 24.
% By weight, melting point (MP), melt index (M
I) and the content of vinyl acetate (VA) are as follows: MP ≧ 120−4.1 [log (MI)] − 1.33 VA (where MP is in ° C., MI is in g / 10 min.) , V
The unit of A is% by weight).
A hot melt composition containing a vinyl acetate copolymer. 2. The compounding amount of the ethylene-vinyl acetate copolymer (I) is 5 to 60 parts by weight, and the ethylene-vinyl acetate copolymer (II)
2. The hot melt composition according to claim 1, wherein the amount of the vinyl acetate copolymer is 95 to 40% by weight. 3. An ethylene-vinyl acetate copolymer (II) is prepared by using a tubular reactor at a polymerization reaction pressure of 235 to 30.
0 MPa, the peak temperature of the polymerization reaction is 200 to 260 ° C., the concentration of the chain transfer agent is 0.2 to 10 mol% based on the total amount of the raw materials supplied to the reactor, and the amount of the radical generating catalyst is based on the total amount of the raw materials supplied to the reactor. Concentration is 1 to 50 weight p
3. The hot melt composition according to claim 1, which is polymerized under pm conditions. 4. A hot melt composition according to claim 1, wherein the hot melt composition is 200 parts by weight.
A hot melt composition comprising up to 150 parts by weight of a tackifier and / or up to 150 parts by weight of a wax.