JP2003327942A - Hot melt adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hot melt adhesive composition excellent in recycling aptitude, easy to remove by using a filter in defibrating waste pulp without pulverizing. <P>SOLUTION: The hot melt adhesive composition containing a base polymer, a tackifier resin and a wax component as the essential components, manifests elongation of ≥500% and tensile strength of ≥10 MPa both at 0°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot melt adhesive composition which is useful in applications such as bookbinding and packaging materials. More specifically, the present invention relates to a hot melt adhesive composition that does not become an obstructive factor when recycling a bookbinding material, a packaging material or the like obtained by using the adhesive composition.

[0002]

2. Description of the Related Art In recent years, recycling of resources has been promoted, and used paper pulp such as used books and corrugated cardboard is collected and recycled to be recycled as recycled paper. The problem is the adhesive used for the recovered used books and cardboard boxes.
That is, as the adhesive, a hot melt adhesive is usually used, but if the adhesive is mixed in during the regeneration process,
The adhesive appears on the recycled paper as stains or spots, which is inconvenient for use as recycled paper. As a method of solving this problem, for example, a method of cutting the part where the adhesive is used and reproducing only the paper part can be considered, but it is very difficult to cut the part where the adhesive is used. It is not a practical method because it complicates the process. Therefore, generally, a method is used in which the recovered waste paper pulp is directly disintegrated using a pulper (paper disintegration device), and only the hot melt adhesive is removed by a filter. However, in this method, since the hot melt adhesive is finely crushed by the pulper to form very fine particles, it may be difficult to completely remove the particles with a filter.

Therefore, a hot-melt adhesive composition for bookbinding intended to suppress fragmentation when disintegrated with a pulper is disclosed in Japanese Patent Application Laid-Open No. 6-80945 and Japanese Patent Application Laid-Open No. 27945/1994.
It is proposed in Japanese Patent No. 24272. Specifically, the former has a tensile strength of 1.96MP at 40 ° C.
a (20 kgf / cm ² ) or more, and the elongation at this time is 200% or more,
Since such an adhesive composition is too hard and easily broken,
In practice, the impact of collision of the stirring blade of the pulper is likely to cause crushing, which may adversely affect the recyclability. The latter is composed of an ethylene-vinyl acetate copolymer resin, a tackifying resin, a wax and an antioxidant, and has a hot melt viscosity in a specific range and an impact strength of 50%.
The breaking height is 1 m or more, and the impact resistance when the stirring blade of the pulper collides is taken into consideration. However, a general-purpose hot-melt adhesive for bookbinding is From the requirement of low temperature flexibility, the impact strength in the above range is usually satisfied, and the adhesive composition of this publication cannot sufficiently prevent fragmentation in the actual disintegration treatment with a pulper. .

On the other hand, as another means for enabling removal by a filter or the like, it is possible to make the hot-melt adhesive water-soluble, but if water-solubility is imparted, the workability as a hot-melt adhesive decreases, so Actually, it is difficult to impart water solubility, and in this case, since the hot melt adhesive is mixed in the regenerated liquid, treating this as a waste liquid causes a problem of environmental pollution, and the waste liquid The processing is expensive.

[0005]

Therefore, the present invention provides a hot melt adhesive composition having excellent recyclability, which is easy to remove by a filter without fragmentation in the disintegration treatment of waste paper pulp. With the goal.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that in order to prevent fragmentation of the hot melt adhesive when disintegrating waste paper pulp with an actual pulper. Found that it is important that the fracture energy (elongation rate and tensile strength) in the low temperature region be above a certain level, and arrived at the present invention. The hot melt adhesive composition according to the present invention is a hot melt adhesive composition containing a base polymer, a tackifying resin and a wax component as essential components, and has an elongation of 500 at 0 ° C.
% Or more and a tensile strength of 10 MPa or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The hot-melt adhesive composition of the present invention has an elongation at 500C of not less than 500% and a tensile strength of 10%.
It is important that the pressure is at least MPa. By setting the breaking energy (elongation rate and tensile strength) in the low temperature region to be equal to or higher than a certain level, it is possible to effectively suppress fragmentation of waste paper pulp in the disaggregation process. 0 ° C
Elongation at less than 500% or 0 ° C
If the tensile strength is less than 10 MPa, the adhesive will be shredded during disaggregation. In order to satisfy the elongation rate and the tensile strength within the above ranges, for example, a polymer having excellent low temperature characteristics as described below may be selected as a base polymer which is an essential component. The elongation rate and tensile strength can be measured, for example, by the methods described later in Examples.

The hot melt adhesive composition of the present invention contains a base polymer as an essential component. Examples of the base polymer include polyolefins such as polyethylene and polypropylene, amorphous polyolefins, ethylene-
Examples thereof include unsaturated acid copolymers, styrene thermoplastic elastomers, polyisobutylene, polyesters, polyamides and polyurethanes. Among these, ethylene-
Polymers having excellent low-temperature characteristics such as unsaturated acid copolymers are preferable, and specifically, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene- It is preferably one or more selected from the group consisting of 2-ethylhexyl acrylate copolymer. In addition, the MF of these base polymers
R is preferably 400 or less. The base polymer may be used alone or in combination of two or more.

The content of the base polymer in the hot melt adhesive composition of the present invention is not particularly limited, but is 4
It is preferably 0% by weight or more. If it is less than 40% by weight, the elongation in the low temperature region tends to decrease.
The hot melt adhesive composition of the present invention contains a tackifying resin as an essential component. The tackifying resin is not particularly limited, and examples thereof include rosin-based adhesive resins such as rosin and rosin ester, petroleum-based adhesive resins obtained by polymerizing C5 fraction and C9 fraction of petroleum, β-pinene and limonene. Examples thereof include terpene-based adhesive resins obtained by polymerizing the above. The tackifying resins may be used alone or in combination of two or more.

The content of the tackifying resin in the hot melt adhesive composition of the present invention is not particularly limited, but is 30
It is preferably ˜50% by weight. If it is out of the above range, the elongation in the low temperature region tends to decrease. The hot melt adhesive composition of the present invention contains a wax component as an essential component. Examples of the wax component include petroleum waxes such as paraffin wax and micro wax; synthetic waxes such as polyethylene wax and polypropylene wax; and the like. Among them, the synthetic wax is particularly preferable from the viewpoint of improving tensile strength. preferable. The wax component may be used alone or in combination of two or more.

The content of the wax component in the hot melt adhesive composition of the present invention is not particularly limited, but may be 5 to 5.
It is preferably 20% by weight. When it is out of the above range, the elongation percentage and the tensile strength tend to be low. The hot melt adhesive composition of the present invention may also contain a plasticizer. Examples of the plasticizer include liquid paraffin; paraffin-based, naphthene-based, or aromatic process oils; liquid resins such as liquid polybutene, liquid polyisobutylene, and liquid polyisoprene; and the like. The plasticizer may be used alone or in combination of two or more.

The content of the plasticizer in the hot melt adhesive composition of the present invention is not particularly limited, but is preferably 0 to 15% by weight. If it is out of the above range, the tensile strength tends to be low. The hot melt adhesive composition of the present invention may contain conventionally known additives such as an antioxidant and a colorant, if necessary. Examples of the antioxidant include phenol-based, thioether-based, and phosphite-based antioxidants, and examples of the colorant include:
For example, titanium oxide and the like can be mentioned. These additives are 1
Only one species may be used, or two or more species may be used in combination.
The content of these additives in the hot melt adhesive composition of the present invention may be set appropriately and is not particularly limited.

The adhesive composition of the present invention has a softening point of 100.
It is preferably at least ° C. Thereby, even if the adhesive composition leaks from the filter and is mixed during the recycling process of the waste paper pulp, it is possible to prevent spreading of spots or spots on the recycled paper by the heating roll. The adhesive composition of the present invention preferably has a melt viscosity of 3000 to 8000 mPa · s at 180 ° C., for example.
If it deviates from this range, roll suitability may be deteriorated. The adhesive composition of the present invention can be obtained by mixing the above-mentioned base polymer, tackifying resin and wax component and, if necessary, additives such as an antioxidant and a colorant. Preferably, first, a wax component, a part of the tackifying resin, and an additive such as an antioxidant or a coloring agent are mixed, and then a base polymer is mixed therewith, and then the balance of the tackifying resin is added to the composition. It may be mixed.
Moreover, it is preferable to mix the components in a molten state within a temperature range of about 130 to 200 ° C.

The adhesive composition of the present invention can be used as a hot melt adhesive as it is or as an intermediate of a hot melt adhesive. When it is used as an intermediate of an adhesive, other components may be further compounded until the adhesive is used as the final product.

[0015]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. The physical properties of the adhesive compositions obtained in Examples and Comparative Examples were measured and evaluated as follows. <Melt viscosity and softening point> Measured according to Japan Adhesive Industry Association Standard JAI7. <Elongation rate, tensile strength> According to Japan Adhesive Industry Association Standard JAI7, dumbbell No. 2 was used to measure at 0 ° C.

<Recyclability-1 (Passage)> About 1 g of the obtained adhesive composition was used to prepare three hot melt sheets having a size of 30 mm × 30 mm and a thickness of 1.2 mm, and the total weight (a) was measured. I had it. Next, mixer (Co., Ltd.)
(Made by Nakasa Co., Ltd.) was charged with 500 mL of water at 30 ° C., three sheets were further added, and the mixture was stirred for 3 minutes, then 1.0
It was filtered with a mm filter. Next, the residue after filtration was filtered with running water for 5 minutes, and then dried in a thermostatic bath at 40 ° C. for 30 minutes, and the weight (b) of the obtained residue was measured. Then, the passage rate of the adhesive composition that passed through the filter was calculated by the following formula. Passage rate (% by weight) = [100− (a−b) / a] × 10
0 <Recycling suitability-2 (number of spots)> The method was based on the research report on ideal bookbinding for used paper recycling magazine. That is, three hot melt sheets having a size of 30 mm × 30 mm and a thickness of 0.8 ± 0.02 mm were produced using the obtained adhesive composition. Then, using a TAPPI standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.), water 2 at 30 ± 3 ° C.
L and an aqueous solution of sodium hydroxide having a sodium hydroxide concentration of 50 g / L were added, and the waste paper AD was used.
Rotate at 3000 rpm by adding 50g and 3 sheets.
Disaggregation was performed for 30 minutes at rpm. Next, the slurry obtained by the disaggregation treatment was treated with a 10-cut flat screen at a water flow of 10 L / min for 5 minutes, and the accept component was recovered by a wire having an opening of 100 μm or less (150 mesh or more) (the reject component was discarded). After diluting the recovered accepting component with water so that the total amount becomes 5 L, this was treated with a 6-cut flat screen at a water flow of 10 L / min for 6 minutes to collect the rejected component, and while the rejected component was diluted with water, the residue was retained. The mixture was suction-filtered using a Buchner funnel so as to be uniform. After filtering, the filter paper obtained is 105
After predrying at ℃ for 30 seconds, stack one sheet of PPC paper,
It was treated with a rotary dryer at 120 ° C. for 2 minutes. Then, the number of oily spots attached to the PPC paper was visually counted.

Example 1 As a base polymer, ethylene / vinyl acetate (72/28 weight ratio) copolymer (MFR
400) 30 parts by weight, and ethylene / vinyl acetate (6
0/40 weight ratio) 20 parts by weight of copolymer (MFR60),
30 parts by weight of a rosin ester as a tackifying resin, 20 parts by weight of a polyethylene wax (“Paraflint H1” manufactured by Sazol Co., Ltd.) as a wax component, and 1 part by weight of titanium oxide were placed in a stainless beaker and mixed at 160 ° C., A hot melt adhesive composition was obtained. The melt viscosity, softening point, elongation at 0 ° C. and tensile strength of the obtained adhesive composition are shown in Table 1. In addition, Table 1 also shows the results of evaluation of recyclability performed using the obtained adhesive composition.

Example 2 The base polymer used in Example 1 was prepared by using 30 parts by weight of ethylene / ethyl acrylate (75/25 weight ratio) copolymer (MFR250) and ethylene / ethyl acrylate (65/35 weight ratio). ) A hot melt adhesive composition was obtained in the same manner as in Example 1 except that the amount of the copolymer (MFR30) was changed to 20 parts by weight. The melt viscosity, softening point, elongation at 0 ° C. and tensile strength of the obtained adhesive composition are shown in Table 1. In addition, Table 1 also shows the results of evaluation of recyclability performed using the obtained adhesive composition.

Comparative Example 1 The base polymer in Example 1 was changed to 40 parts by weight of ethylene / vinyl acetate (72/28 weight ratio) copolymer (MFR150), and the amount of rosin ester used as a tackifying resin. Was changed to 40 parts by weight, and a hot melt adhesive composition was obtained in the same manner as in Example 1. The melt viscosity, softening point, elongation at 0 ° C. and tensile strength of the obtained adhesive composition are shown in Table 1.
Shown in. In addition, Table 1 also shows the results of evaluation of recyclability performed using the obtained adhesive composition.

[0020]

[Table 1]

[0021]

The hot melt adhesive composition of the present invention comprises:
It has excellent recyclability, does not shred in the disintegration treatment of waste paper pulp, and is easily removed by a filter. Therefore, recycled paper pulp can be efficiently recycled without becoming an obstacle when recycling the bookbinding, the packaging material and the like obtained by using the hot melt adhesive composition of the present invention.

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Claims (4)

[Claims] 1. A hot melt adhesive composition containing a base polymer, a tackifying resin and a wax component as essential components, which has an elongation at 500C of not less than 500% and a tensile strength of not less than 10 MPa. Hot melt adhesive composition. 2. The hot melt adhesive composition according to claim 1, which also contains a plasticizer. 3. The base polymer is selected from the group consisting of an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-2-ethylhexyl acrylate copolymer. The hot melt adhesive composition according to claim 1 or 2, which is one or more of the following. 4. The hot melt adhesive composition according to claim 1, which has a softening point of 100 ° C. or higher.