JPH0892359A - Biodegradable polyester adhesive - Google Patents

Abstract

PURPOSE: To obtain the subject adhesive containing each specific proportion of lactic acid residue and caprolactone residue, and also containing a biodegradable polyester with specific reduced viscosity, stable in quality, excellent in water resistance, presenting high bond strength, thus useful for bonding biodegradable base materials. CONSTITUTION: This adhesive contains 60-95 (pref. 65-90) mol% of lactic acid residue of formula I [the molar ratio of L-lactic acid to D-lactic acid (L/D) being 1-9], 5-30 (pref. 10-20) mol% of caprolactone residue of formula II, and also contains a biodegradable polyester 0.5-1.5 (pref. 0.6-1.3) dL/g in reduced viscosity (ηSP/c). It is preferable that the biodegradable polyester also contain respective residues of oxy acid(s), succinic acid, propylene glycol and/or glycerin. This biodegradable polyester is obtained, for example, by melt blending of a lactide, i.e., lactic acid dimer, and caprolactone followed by ring opening polymerization using a relevant catalyst.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to biodegradable polyester adhesives. More specifically, it relates to a biodegradable polyester adhesive used as an adhesive for a biodegradable substrate such as a biodegradable film, a biodegradable nonwoven fabric or paper.

[0002]

2. Description of the Related Art Due to the increasing awareness of environmental problems in recent years, products using natural materials or biodegradable synthetic materials have been actively developed. In these products, there are more opportunities for adhering biodegradable substrates such as biodegradable films, biodegradable non-woven fabrics and papers, and there is an increasing demand for biodegradable adhesives.

Conventionally, as a biodegradable adhesive, a starch paste, a natural material such as glue, or a PVA (polyvinyl alcohol) type synthetic resin has been used. However, although these adhesives have biodegradability, they have drawbacks such as unstable quality, poor water resistance, and low adhesive strength.

It is an object of the present invention to provide a biodegradable polyester adhesive having a stable quality, excellent water resistance and high adhesive strength as compared with conventional biodegradable adhesives, in which the above problems are solved. Is.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found the following biodegradable polyester adhesive and completed the present invention.

That is, in the present invention, the lactic acid residue is 60 to 95 mol% [however, the molar ratio of L-lactic acid to D-lactic acid (L / D) is 1 to 9], and the caprolactone residue is 5 to 30 mol%. %, And a biodegradable polyester adhesive having a reduced viscosity (η _{SP / C} ) of 0.5 to 1.5 dl / g. Also, the present invention
The present invention relates to the above biodegradable polyester adhesive in which a residue of oxyacid other than lactic acid and caprolactone, succinic acid, propylene glycol or glycerin is contained in the biodegradable polyester.

The biodegradable polyester in the present invention is
The following formula

[0008]

[Chemical 1]

It is necessary to contain 60 to 95 mol% of the lactic acid residue represented by
It is preferably 65 to 90 mol%. 60-95 mol%
Within the range, good adhesive strength and biodegradability can be obtained.

The molar ratio of L-lactic acid and D-lactic acid (L / L
It is also necessary that D) is 1 to 9, preferably 1 to
It is 3. When L / D exceeds 9, the solubility of the polyester in an organic solvent becomes poor, and L / D is less than 1 (D
-Lactic acid excess) increases the raw material cost. As lactic acid, any of L-lactic acid, D-lactic acid and DL-lactic acid can be used.

Further, the biodegradable polyester in the present invention has the following formula

[0012]

[Chemical 2]

The caprolactone residue represented by
It is necessary to contain 30 mol%, preferably 10 to 20 mol%. Within the range of 5 to 30 mol%, good adhesive strength can be obtained, and good workability can be obtained even when used as a hot melt adhesive.

The lactic acid residue and the caprolactone residue alone make up 100 mol% or less of the whole polyester.

As the biodegradable polyester, in addition to lactic acid and caprolactone, compounds having biodegradability such as oxyacids other than lactic acid and caprolactone, succinic acid, propylene glycol or glycerin can be used. In this case, the biodegradable polyester can be obtained by copolymerizing lactic acid and caprolactone with the compound. Moreover, the said compound can be used also by 1 type (s) or 2 or more types. The residue of the compound having biodegradability other than lactic acid and caprolactone can be contained in an amount of 35 mol% or less of the total polyester, but may be 0%.

Examples of oxy acids other than lactic acid and caprolactone include glycolic acid, 2-hydroxyisobutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 16-
Examples thereof include hydroxyhexadecanoic acid, 2-hydroxy-2-methylbutyric acid, 10-hydroxystearic acid, malic acid, citric acid and gluconic acid.

The reduced viscosity of the biodegradable polyester (η
_{SP / C} ) is required to be 0.5 to 1.5 dl / g, preferably 0.6 to 1.3 dl / g. 0.5
If it is less than dl / g, good adhesive strength cannot be obtained.
If it exceeds 5 dl / g, good coating suitability cannot be obtained. The reduced viscosity is, for example, polymerization time of polyester, polymerization temperature,
It can be adjusted by changing the degree of pressure reduction (when polymerizing while reducing pressure) or by changing the amount of the alcohol component used as a copolymerization component. The reduced viscosity was measured at a sample concentration of 0.125 g / 25
It is a value measured using an Ubbelohde viscous tube at ml, a measurement solvent chloroform, and a measurement temperature of 25 ° C.

The method for producing the biodegradable polyester is not particularly limited, and a conventionally known method can be used. For example, a method in which lactide, which is a dimer of lactic acid, and caprolactone are melt-mixed and subjected to ring-opening polymerization by heating using a known ring-opening polymerization catalyst (eg, tin octylate, aluminum acetylacetonate, etc.), heating and decompression. The method of directly performing dehydration polycondensation by Also,
The biodegradable polyester can be produced as described above using lactide and caprolactone, which are dimers of lactic acid, and the biodegradable compound other than lactic acid and caprolactone.

The biodegradable polyester adhesive of the present invention is
There is no particular limitation as long as it contains the biodegradable polyester, and a solvent-based adhesive or a hot melt adhesive may be used.

When used as a solvent type adhesive, examples of the solvent used include ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone and cyclohexanone, and aromatic solvents such as toluene and xylene. In addition, after dissolving the biodegradable polyester in the solvent, it can be applied by a roll coater, a spray, a dipping method, or another method, dried, melted, and adhered.

When used as a hot melt adhesive, in addition to the above biodegradable polyester, a flow control agent, a plasticizer,
By adding a filler or the like, it is possible to improve the flow characteristics, the adhesive characteristics and the like at the time of heating and melting. In addition, a hot melt adhesive or the like can be used to apply and bond the hot melt adhesive to an object.

The biodegradable polyester adhesive of the present invention is particularly preferably used when adhering a biodegradable substrate such as a biodegradable film, a biodegradable nonwoven fabric or paper.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 L-lactide (100 g), DL-lactide (100 g), caprolactone (30 g) and tin octylate (50 mg) were added to the flask, and ring-opening polymerization was performed at 190 ° C. for 1 hour in a nitrogen atmosphere to obtain polyester A. . Next, 100 g of the above polyester was dissolved in 200 g of methyl ethyl ketone to obtain an adhesive.

Example 2 L-lactide (100 g), DL-lactide (100 g), caprolactone (50 g), glycerin (0.5 g) and tin octylate (50 mg) were added to a flask, and the mixture was stirred under a nitrogen atmosphere at 190 g.
Polyester B was obtained by heating ring-opening polymerization at 1 ° C. for 1 hour. Also, an adhesive was obtained in the same manner as in Example 1.

Comparative Example 1 100 g of L-lactide, 100 g of DL-lactide, 30 g of caprolactone, 3 g of propylene glycol, and 50 mg of tin octylate were added to a flask and, under a nitrogen atmosphere,
Polyester C was obtained by heating ring-opening polymerization at 190 ° C for 1 hour.
Got Also, an adhesive was obtained in the same manner as in Example 1.

Comparative Example 2 L-lactide (50 g), DL-lactide (50 g), caprolactone (200 g) and tin octylate (50 mg) were added to the flask, and ring-opening polymerization was performed at 190 ° C. for 1 hour in a nitrogen atmosphere to obtain polyester D. . Also, an adhesive was obtained in the same manner as in Example 1.

Comparative Example 3 An adhesive was obtained in the same manner as in Example 1 using Byron GK140 (manufactured by Toyobo Co., Ltd.) which is a polyester adhesive (containing no lactic acid).

Table 1 shows the composition and physical properties of the polyesters used in the above Examples and Comparative Examples. The reduced viscosity was measured using a Ubbelohde viscosity tube at a sample concentration of 0.125 g / 25 ml, a measurement solvent of chloroform, and a measurement temperature of 25 ° C.

[0030]

[Table 1]

Experimental Example The adhesives obtained in the above Examples and Comparative Examples were applied on a polylactic acid film (thickness 30 μm) to a dry thickness of 5 μm, dried and then laminated with paper (thickness 200 μm).
Bonded at 80 ° C. Using this laminated sample,
The adhesive strength and biodegradability were evaluated as follows.
Table 2 shows the results.

Adhesive Strength Using the above-mentioned laminated sample of 2.5 cm × 10 cm, T peel was measured by Tensilon (manufactured by Orientec Co., Ltd.) under the conditions of a pulling speed of 200 mm / min, 23 ° C. and 60% RH. Biodegradability 10 cm x 10 cm of the above-mentioned laminated sample was placed in a composter (raw trash processing machine, "MAM" manufactured by Mitsui Home Co., Ltd.), and after 7 days, the morphology (degree of decomposition) of the sample was visually observed, and the following criteria were used. Was evaluated according to. ◯: The image of the sample is completely absent: Δ: Fragment of the sample is present ×: The image of the sample remains almost

[0033]

[Table 2]

The biodegradable adhesives of Examples 1 and 2 were stable in quality. Further, the water resistance test was performed on the laminated samples of the biodegradable adhesives of Examples 1 and 2 (the sample was immersed in water at 25 ° C. for 24 hours, then taken out and dried, and the adhesive strength of the sample was adjusted as described above. The adhesive strength retention rate is 90%.
The above results (compared to before immersion in water) were good. On the other hand, when a similar water resistance test was conducted with starch paste,
It has already peeled off during immersion in water.

[0035]

Industrial Applicability The biodegradable polyester adhesive of the present invention has stable quality, excellent water resistance, high adhesive strength, biodegradable film, biodegradable nonwoven fabric or It is useful as an adhesive for biodegradable substrates such as paper.

Front page continued (72) Inventor Tomohiro Aoyama 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Co., Ltd. (72) Inventor Minako Arita 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Inside Research Institute, Inc. (72) Inventor Kiyofumi Horita 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Co., Ltd. Inside Research Institute (72) Keiichi Uno 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Koki Co., Ltd.

Claims (2)

[Claims] 1. A lactic acid residue of 60 to 95 mol% [however, L
-Lactic acid and D-lactic acid have a molar ratio (L / D) of 1 to 9], a caprolactone residue of 5 to 30 mol% and a reduced viscosity (η _{SP / C} ) of 0.5 to 1.5 dl / g. A biodegradable polyester adhesive characterized by containing a biodegradable polyester which is 2. The biodegradable polyester adhesive according to claim 1, wherein the biodegradable polyester contains a residue of oxy acid other than lactic acid and caprolactone, succinic acid, propylene glycol or glycerin.