JPH08277382A - Hot-melt adhesive composition - Google Patents

Abstract

PURPOSE: To obtain a hot-melt adhesive composition comprising a prescribed synthetic rubber, a tackifier resin and a plasticizing, oil as essential components, excellent in adhesiveness and thermal stability, suitable for a hygienic material such as paper diaper, sanitary napkin, etc. CONSTITUTION: This hot-melt adhesive composition comprises (A) preferably 20-30wt.% of a synthetic rubber component containing a styrene-ethylene- propylene-styrene block copolymer, (B) preferably 55-65wt.% of a tackifier resin component such as a (modified) rosin-based resin, etc., and (C) preferably 7-22wt.% of a plasticizing oil component such as a paraffinic component, etc., as essential components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot melt adhesive composition used for assembling sanitary materials such as disposable diapers and sanitary napkins, which is particularly excellent in adhesiveness and thermal stability. It relates to a composition.

[0002]

2. Description of the Related Art Hot melt adhesives are usually used for assembling sanitary materials such as disposable diapers and sanitary napkins. Such hot-melt adhesives are soft and white or colorless and odorless, and have low adhesiveness to polyethylene films, polyurethane foams, polyurethane films, natural rubber, woven fabrics, non-woven fabrics, etc. to be adhered from low temperatures. Being excellent at high temperatures,
It is required as an important performance that coloration and viscosity change due to heating are small. However, in the actual situation, there is no conventional hot melt adhesive that is excellent in satisfying all the above requirements. For example, as a hot melt adhesive, recently, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-
A rubber-based hot melt adhesive obtained by using a synthetic rubber material having a soft texture such as butylene-styrene block copolymer (SEBS) as a polymer base and adding a tackifying resin and a plasticizing oil thereto is widely used. But
The above-mentioned SIS-based one has excellent adhesiveness but extremely poor thermal stability, and the SBS-based one has relatively good thermal stability but poor adhesiveness.
There is no one based on BS, which has both thermal stability and adhesiveness, such as excellent thermal stability but poor adhesiveness.

[0003]

Therefore, when adhesiveness is particularly required, SIS alone base is used, and when heat stability is particularly required, SEBS alone base is used. If both adhesiveness and thermal stability are required at the same time, use SBS alone base or SEB
Although the inventors have devised such as using a blend of S and SIS, they still retain their respective drawbacks, and a satisfactory hot melt adhesive has not always been obtained.

The present invention has been made in view of such circumstances, and can be a hot-melt adhesive having excellent performance which simultaneously satisfies both adhesiveness and thermal stability, which have not been compatible with each other. The purpose is to provide a composition.

[0005]

In order to achieve the above object, the present invention comprises a synthetic rubber component, a tackifying resin component and a plasticizing oil component as essential components, and the synthetic rubber component contains styrene-ethylene- The gist is a hot-melt adhesive composition containing a propylene-styrene block copolymer (SEPS).

That is, the present inventors have conducted a series of studies in order to obtain an adhesive composition which simultaneously satisfies both adhesiveness and thermal stability, which have hitherto been incompatible. As a result, it was found that when a synthetic rubber component containing SEPS is used as the base of the hot melt adhesive composition, a hot melt adhesive excellent in both adhesiveness and thermal stability can be obtained. It was

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described.

The hot melt adhesive composition of the present invention comprises:
A synthetic rubber component, a tackifying resin component, and a plasticizing oil component are essential components.

As the synthetic rubber component, it is necessary to use one containing SEPS. Above SEPS
Is a copolymer in which an ethylene structure and a propylene structure are mixed in the middle of the styrene polymer blocks at both ends, and a styrene phase functions as a hard segment and an ethylene-propylene phase functions as a soft segment. It is of structure. This SEPS is, for example, a styrene-isoprene-styrene block copolymer (SI
It can be easily obtained by hydrogenating the isoprene polymer part of S). However, when used in the present invention, the SEPS has a styrene content of 10 to 35.
It is preferable to use one having a weight% (hereinafter abbreviated as “%”). This is because if the styrene content is less than 10%, the adhesiveness at high temperatures tends to be inferior, and if it exceeds 35%, the adhesiveness at low temperatures tends to be poor. And, the compounding amount of the SEPS is 10 with respect to the whole composition.
-50%, preferably 15-35%, more preferably 20-30%. If the blending amount of SEPS is too small, the adhesiveness will be poor, and if it is too large, the texture will be hard and the melt viscosity will be high and the coating workability will tend to be poor.

On the other hand, the tackifying resin component may be any as long as it is used in a usual hot melt adhesive composition, but it has a low molecular weight and wets the composition. It is necessary to improve the adhesiveness and at the same time provide an initial adhesive force to lower the viscosity of the entire composition to improve the workability of applying the adhesive. And
It is preferably colorless or white and odorless. Examples of such a tackifying resin component include hydrogenated aromatic petroleum resin, hydrogenated aliphatic petroleum resin,
Hydrogenated terpene resins are preferred. Further, rosin resin, modified rosin resin, terpene resin, modified terpene resin modified by a method other than hydrogenation, aliphatic petroleum resin, aromatic petroleum resin, aliphatic-aromatic petroleum resin, Examples include styrene-based petroleum resins. All of these resins are SE used as the synthetic rubber component.
Since it has excellent compatibility with PS, it can obtain a wide range of adhesion from low temperature to high temperature, and at the same time, it has excellent thermal stability because it has no double bond in its chemical structure. The softening temperature of the above resin is not particularly limited, and it may be solid or liquid at room temperature, but liquid is preferable because it has an effect as a plasticizer. Further, the amount of the tackifying resin component is too large, the texture becomes hard and the low-temperature adhesiveness becomes extremely poor, and if the amount is too small, the wettability to the adherend decreases and the initial adhesive strength becomes poor, The compounding amount of at least one tackifying resin component is 40 to 70.
%, Preferably 50 to 70%, more preferably 55 to
It is preferable to set it to 65%.

The plasticizing oil component may be any one as long as it is used in a usual hot melt adhesive composition, but it has a lower molecular weight than the tackifying resin component. It is preferable that they serve as a viscosity modifier, improve the low temperature tackiness, and soften the composition. As such a plasticizing oil component, an oil in which a paraffin-based component, a naphthene-based component, and an aromatic-based component are mixed is usually used. However, when the amount of the paraffin-based component is increased, the thermal stability is improved and the naphthene-based component is improved. When the content of the components is increased, the low temperature adhesiveness is improved. When the amount of the plasticizing oil is too small, the texture becomes hard and the low temperature adhesiveness decreases, and when the amount is too large, the high temperature adhesiveness decreases, so that 3 to 50%, preferably 5 to 30%,
It is more preferable to set it to 7 to 20%.

The hot melt adhesive composition of the present invention may contain various additives used in conventional hot melt adhesive compositions, in addition to the above-mentioned essential components.
Examples of such additives include hindered phenol-based stabilizers for improving heat resistance, oxidation resistance, and light stability, and ultraviolet absorbers. When using the hindered phenol-based stabilizer, it is preferable to set the compounding amount thereof to 0.1 to 1%. When the above-mentioned ultraviolet absorber is used, its blending amount is 0.1-0.1%.
It is preferable to set it to 0.5%.

Further, other synthetic rubber components or resin components used in conventional hot melt adhesive compositions may be used for the purpose of adjusting flexibility, wettability, adhesiveness, melt viscosity, softening point and reducing cost. You may mix. Examples of such optional components include synthetic rubbers such as SIS and SBS, ethylene copolymers such as ethylene-vinyl acetate copolymers and ethylene-ethyl acrylate copolymers, atactic polypropylene, isotactic polypropylene, propylene- Examples thereof include olefin resins such as 1-butene copolymer and propylene-1-butene-ethylene terpolymer. Further, softening agents such as liquid polybutene, liquid polyisobutylene, liquid polyisoprene, etc. may be added. In addition, the blending amount when using these optional components is usually
20% or less for colorless or white, 15% for colored
The following setting is preferable. Since these optional components tend to interfere with the excellent properties obtained by the above-mentioned essential components, it is desirable to use them in a controlled amount.

The hot melt adhesive composition of the present invention comprises:
For example, it can be obtained by putting each of the above-mentioned raw materials in a melt-stirring mixer and mixing them by heating.

Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to these embodiments.

[0016]

Examples 1 to 6 The raw materials shown in Tables 1 and 2 below were blended according to the following composition and melt-kneaded at about 150 ° C. to obtain the desired hot-melt adhesive composition.

[0017]

[Table 1]

[0018]

[Table 2]

Then, the characteristics of each of the above-mentioned examples were tested by the following methods, and the results are shown in Table 3 below.

<Melt Viscosity> The melt viscosity was measured using a Brookfield Thermocell (manufactured by Brookfield).

<Adhesiveness> A polyethylene film and a non-woven fabric, which are mainly used for paper diapers, or a non-woven fabric and a non-woven fabric, are adhered by using the above-mentioned example product or comparative example product (application temperature 120 to 150 ° C., application amount 0. 05g / 5
cm ² , beaded). This was left for 24 hours in a temperature atmosphere of 10 ° C. and 40 ° C., taken out, and the adherend was peeled off by hand, and when the material was broken, was evaluated as ◯, when interfacial peeling was evaluated as ×, and the middle was evaluated as Δ.

<Thermal Stability> Viscosity Reduction Rate First, the above-mentioned Example product and Comparative Example product were left for 72 hours in a temperature atmosphere of 180 ° C., and the viscosity before and after that was measured to calculate the viscosity reduction rate Was used as an index of thermal stability. That is, the calculation formula is as follows.

[0023]

[Equation 1] V: Melt viscosity of the hot melt adhesive composition at 160 ° C. after standing at 180 ° C. for 72 hours Vo: Melt viscosity of the hot melt adhesive composition at 160 ° C. before being subjected to heat history

Hue In addition, the hot melt adhesive composition was allowed to stand in a temperature atmosphere of 180 ° C. for 72 hours, and the hue of the composition at that time was visually determined. The case of completely colorless or white was marked with ⊚, the case of almost colorless or close to white was marked with ◯, the case of slightly colored was marked with Δ, and the case of clearly colored was marked with x.

Odor Similarly, the hot melt adhesive composition was allowed to stand in a temperature atmosphere of 180 ° C. for 72 hours, and the odor of the composition at that time was evaluated by a sensory test (10 panelists). ◎: completely odorless, ○: almost odorless, Δ: slight odor, X: obvious odor

[0026]

[Table 3]

[0027]

[Comparative Examples 1 to 4] Four kinds of hot melt adhesive compositions for sanitary materials which are currently sold in the market and have different kinds of resin components were prepared. Their compositions are shown in Table 4 below. Then, the characteristics of each of the comparative examples were evaluated in the same manner as in the above example. The results are shown in Table 5 below.

[0028]

[Table 4]

[0029]

[Table 5]

From the results shown in Table 5 above, the comparative example products show unfavorable characteristics in any of the items of adhesiveness and heat stability. On the other hand, as shown in the results of Table 3 above, it is understood that the example products exhibit excellent properties in all items.

[0031]

INDUSTRIAL APPLICABILITY As described above, the hot melt adhesive composition of the present invention exhibits excellent adhesiveness and thermal stability, so that it can be applied to polyethylene films, woven fabrics, nonwoven fabrics, etc. A wide range of adhesion can be obtained from low temperature to high temperature on the adherend. In addition, the composition is substantially colorless, does not become colored even when heated, and does not decrease in viscosity. Therefore, it is suitable for use in assembling hygienic materials.

Claims (1)

[Claims] 1. A synthetic rubber component, a tackifying resin component, and a plasticizing oil component as essential components, and the synthetic rubber component contains a styrene-ethylene-propylene-styrene block copolymer. Hot melt adhesive composition.