JP2003048963A - Biodegradable polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable polyester for a biodegradable lamination adhesive and coating agent having stable quality, excellent water resistance and high adhesive strength compared with conventional biodegradable adhesives. SOLUTION: The biodegradable polyester has a lactic acid residue content of 55-95 mol%, a caprolactone residue content of 5-45 mol%, an L-lactic acid to D-lactic acid molar ratio (L/D) of 1-9 in the lactic acid residue and a hydroxy group concentration of 70-500 eq/10<6> g.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable polyester suitable for a biodegradable adhesive. For more details,
The present invention relates to a biodegradable adhesive suitable as a coating adhesive and an adhesive for lamination of biodegradable substrates such as biodegradable film, biodegradable nonwoven fabric, or paper.

[0002]

2. Description of the Related Art With the recent increase in awareness of environmental problems, products using natural materials or biodegradable synthetic materials have been actively developed. In these products, there are more opportunities to bond biodegradable substrates such as biodegradable films, biodegradable nonwoven fabrics, papers and leathers, and there is an increasing demand for biodegradable lamination adhesives.

As a biodegradable adhesive, natural materials such as starch paste and glue, and PVA (polyvinyl alcohol) -based synthetic resins have been studied in the past, but they have the disadvantages of insufficient tackiness and lack of water resistance. Have In addition, acrylic and urethane adhesives for lamination have the drawback that they are not biodegradable.

Further, Japanese Unexamined Patent Publication No. 8-92359 discloses a polylactic acid type adhesive. However, this product has not yet obtained sufficient adhesive strength, or has low crosslinkability when used in combination with a crosslinking agent, resulting in insufficient strength and heat resistance.

An object of the present invention is to solve the above-mentioned problems and to provide a biodegradable adhesive and a coating agent for lamination, which have stable quality, excellent water resistance and high adhesive strength as compared with conventional biodegradable adhesives. To provide a biodegradable polyester for.

[0006]

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 and completed the present invention.

That is, the present invention contains 55 to 95 mol% of lactic acid residues and 5 to 45 mol% of caprolactone residues,
Among the lactic acid residues, the molar ratio of L-lactic acid and D-lactic acid (L / L
D) is 1 to 9 and the hydroxyl group concentration is 70 to 500 equivalents / 10 ⁶ g, which is a biodegradable polyester.

The biodegradable polyester in the present invention is
55-9 lactate residue represented by the following -O-CH (CH ³⁾ -CO- the entire polyester
It is necessary to contain 5 mol%, preferably 6
It is 0 mol% or more. The preferable upper limit is 85 mol% or less, more preferably 80 mol% or less, further preferably 75 mol% or less, and most preferably 70 mol% or less. Within the above range, good adhesive strength and excellent 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 5. If L / D exceeds 9, the solubility of the polyester in a general-purpose solvent may deteriorate, and if L / D is less than 1 (excess of D-lactic acid), raw material costs may increase. As lactic acid, any of L-lactic acid, D-lactic acid and DL-lactic acid can be used, and these are combined to obtain an appropriate L / D.

Further, the biodegradable polyester in the present invention is a caprolactone residue represented by the following formula --O--CH ² --CH ² --CH ² --CH ² --CH ² --CO-- It is necessary to contain 5 to 45 mol% of the total polyester. The lower limit is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 25 mol% or more, and particularly preferably 30 mol% or more. Within this range, good adhesive strength and good biodegradability can be obtained.

The hydroxyl group concentration of the biodegradable polyester in the present invention is in the range of 70 to 500 equivalents / 10 ⁶ g. The lower limit is preferably 100 equivalent / 10 ⁶ g, more preferably 130 equivalent / 10 ⁶ g, further preferably 150 equivalent / 10 ⁶ g, particularly preferably 180 equivalent / 1.
It is 0 ⁶ g. The upper limit is preferably 450 equivalents / 1
0 ⁶ g, more preferably 400 equivalents / 10 ⁶ g, particularly preferably 350 equivalents / 10 ⁶ g, most preferably 300 equivalents / 10 ⁶ g. If it is less than 70 equivalents / 10 ⁶ g, particularly good adhesive strength may not be obtained during lamination. In particular, the adhesive strength when used in combination with a crosslinking agent may be insufficient, or the heat resistance may be insufficient. If it exceeds 500 equivalents / 10 ⁶ g, the water resistance may deteriorate.

Examples of the method for adjusting the hydroxyl group concentration to the above range include a reaction initiator for polymerizing polylactic acid using lactide, a method for adding a polyhydric alcohol compound as an additive during the polymerization, and a method for polymerizing polylactic acid. Then, a method of adding a polyhydric alcohol for depolymerization, a method of reacting with a hydroxy group-containing epoxy compound or the like to introduce a plurality of hydroxyl groups at the terminal end, and the like can be mentioned. The hydroxyl value can be increased by using an oxy acid as a reaction initiator or an additive, but this method is not preferable because the molecular weight decreases as the hydroxyl value increases. As the polyhydric alcohol compound, trihydric or higher polyhydric alcohol compounds are preferable, and grisserine, polyglycerin,
Polyvinyl alcohol, sorbitol, glucose, saccharides such as galactose, trimethylolpropane, pentaerythritol and the like can be mentioned. Among these, polyglycerin is preferable. Polymerization degree of 3 for polyglycerin
Those of -20 are preferable. The degree of polymerization of polyglycerin is 2
If it exceeds 0, water resistance may decrease, and if it is less than 3, adhesiveness and curability may become insufficient.

In the case of polyglycerin, the polyglycerin segment contained in the polyester is preferably 20.
It is preferably not more than 10% by weight, more preferably not more than 10% by weight, further preferably not more than 5% by weight and most preferably not more than 3% by weight. Further, the polyglycerin segment is preferably
It is 0.01% by weight or more, more preferably 0.05% by weight or more, further preferably 0.1% by weight or more, and particularly preferably 0.2% by weight or more. When the polyglycerin segment is 20% by weight or more, the water resistance may decrease, and when it is 0.01% by weight or less, a sufficient hydroxyl group concentration may not be secured.

In addition to lactic acid and caprolactone, for example, an oxy acid other than lactic acid and caprolactone, an aliphatic dicarboxylic acid, and an aliphatic glycol can be copolymerized with the polyester. The residue of the above compounds other than lactic acid and caprolactone can be contained in 20 mol% or less of the polyester, but may be 0%.

Examples of oxyacids other than lactic acid and caprolactone include glycolic acid, 2-hydroxyisobutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 16
-Hydroxyhexadecanoic acid, 2-hydroxy-2-methylbutyric acid, 10-hydroxystearic acid, malic acid,
Examples include citric acid and gluconic acid. Examples of the diol include ethylene glycol, diethylene glycol, propylene glycol and butanediol. Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and aromatic diols such as bisphenol A and alkylene oxide adducts of bisphenol A may be copolymerized in a small amount, but from the viewpoint of biodegradability. Is preferably not included. In addition, in the case of copolymerizing a polyester composed of a dicarboxylic acid and a diol, the mol% is calculated by using the dicarboxylic acid and the diol as individual units.

The reduced viscosity (ηsp /
c) is preferably 0.4 to 1.5 dl / g,
More preferably, it is 0.45-1.0 dl / g.
If it is less than 0.4 dl / g, good adhesive strength may not be obtained, and if it exceeds 1.5 dl / g, good coating suitability may not be obtained. The reduced viscosity can be adjusted, for example, by changing the polymerization time of polyester, the polymerization temperature, the degree of pressure reduction (when polymerizing under reduced pressure), or the amount of the alcohol component used as a copolymerization component. it can. The reduced viscosity is a value 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.

The method for producing the polyester is not particularly limited, and a conventionally known method can be used.
For example, a method in which lactide, which is a lactic acid dimer, and caprolactone are melt-mixed and subjected to heating ring-opening polymerization using a known ring-opening polymerization catalyst (eg, tin octylate, aluminum acetylacetonate) or direct heating and depressurization Examples include a method of performing dehydration polycondensation. Further, using lactide and caprolactone, which are dimers of lactic acid, and a compound having biodegradability other than lactic acid and caprolactone,
The polyester can also be produced as described above.

A crosslinking agent can be used in the biodegradable polyester of the present invention. Examples of the cross-linking agent include polyfunctional isocyanates, epoxy resins, and alkyl etherified formaldehyde resins such as melamine resins. Among these, hexamethylene diisocyanate, its trimer, and aliphatic polyfunctional isocyanates such as isophorone diisocyanate are preferable from the viewpoint of biodegradability. The amount of the cross-linking agent is appropriately determined according to the type of the cross-linking agent and the hydroxyl group concentration of the biodegradable polyester, but is preferably 0.1 to 20 wt% with respect to 100 wt% of the biodegradable polyester. . It is more preferably 0.3% by weight or more, and further preferably 0.5% by weight or more. Further, it is more preferably 10% by weight or less, and further preferably 5% by weight or less.

As the solvent used for applying the polyester, an ether solvent such as tetrahydrofuran, a ketone solvent such as methyl ethyl ketone and cyclohexanone, an ester solvent such as ethyl acetate and butyl acetate,
Examples thereof include aromatic solvents such as toluene and xylene.
In addition, after dissolving the biodegradable polyester in the solvent, it can be applied to an object by a roll coater, a spray, a dipping method, or another method, dried, and then adhered.

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

Examples of the biodegradable film include polycaprolactone film and polylactic acid film. Examples of the biodegradable woven fabric and biodegradable nonwoven fabric include plant fibers such as cotton, hemp, and kenaf, animal fibers such as wool and silk, and polylactic acid fibers. Examples of the paper include Japanese paper, Western paper, cardboard, cardboard and the like. As leather, cow, sheep,
Pigs, goats, deers, etc., and rabbits, foxes, etc.

[0022]

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

Example 1 100 g of L-lactide, 100 g of DL-lactide, 165 g of caprolactone, 3.6 g of polyglycerin having a degree of polymerization of 10 "PGL10 (manufactured by Daicel Chemical Industries, Ltd.), hydroxyl group concentration of 850 KOHmg / g", Tin octylate 50
Add mg to a 4-neck flask, and under a nitrogen atmosphere at 190 ° C
By heating and ring-opening polymerization for 3 hours, a polyester (I) was obtained. The hydroxyl value of the polyester (I) was calculated by calculating the hydroxyl value derived from polyglycerin from the charged amount of polyglycerin and adding the acid value by titration to this. Hydroxyl value derived from polyglycerin is 148 eq / 10 ⁶ g, acid value is 27 e
It was q / 10 ⁶ g. Next, 100 g of the above polyester
Was dissolved in 200 g of methyl ethyl ketone, and then the aliphatic isocyanate "Duranate TPA-10" was used.
0 (manufactured by Asahi Kasei Co., Ltd.) was blended to obtain an adhesive.

Comparative Example 1 100 g of L-lactide, 100 g of DL lactide, 165 g of caprolactone and 50 mg of tin octylate were added to a four-necked flask, and ring-opening polymerized by heating at 190 ° C. for 3 hours in a nitrogen atmosphere to give polyester (II). Got Next, 100 g of the above polyester is mixed with 200 g of methyl ethyl ketone.
1 g of "Duranate TPA-100 (manufactured by Asahi Kasei Co., Ltd.)" was added thereto to obtain an adhesive. The acid value of polyester (II) was 40 eq / 10 ⁶ g.

Examples 2 and 3 and Comparative Example 2 Polyglycerin having a degree of polymerization of 10 was 1.2 each.
g, 10.5 g, and 13.4 g, polyesters (III), (IV), and (V) were obtained in the same manner as in Example 1, and an adhesive was obtained in the same manner as in Example 1. Example 2, Example 3, and Comparative Example 2 were made in order, respectively.

Comparative Example 3 76.3 g of L-lactide, 76.3 g of DL-lactide,
241 g of caprolactone, 3.6 g of polyglycerin having a degree of polymerization of 10 and 50 mg of tin octylate were added to a 4-neck flask, and ring-opening polymerization was performed at 190 ° C. for 3 hours under a nitrogen atmosphere to obtain a polyester (VI). . Next, 100 g of the above polyester is dissolved in 200 g of methyl ethyl ketone, and then 1 g of "Duranate TPA-100 (manufactured by Asahi Kasei)" which is an aliphatic isocyanate is blended,
An adhesive was obtained.

[0027]

[Table 1]

Evaluation The adhesives obtained in the above Examples and Comparative Examples were applied on a polylactic acid film (thickness 50 μm) at a dry thickness of 5 μm, dried and then laminated with paper (thickness 2 mm).
Aged at 0 ° C. for 24 hours. The adhesive strength and biodegradability were evaluated. The results are shown in Table 2.

(1) Adhesive strength Using the above-mentioned laminated sample 2.5 cm × 10 cm,
The 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. (2) Biodegradability 10 cm × 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 (decomposition rate) of the sample was visually observed, It evaluated according to the following criteria. ◯: The shape of the sample is completely absent: Δ: Fragment of the sample is present ×: Almost the shape of the sample remains (3) Immerse the adhesive coated film before lamination with water resistant paper in water 2
It was left at 5 ° C for 1 hour. It evaluated according to the following criteria. ◯: No change in sample Δ: Lightly whitened or swollen ×: Whitened or swollen (4) Gel fraction adhesive was coated on a poly (L-lactic acid) film at a dry film thickness of 50 μm, and after drying at 60 ° C. for 5 hours A curing reaction was performed to obtain a film for measuring gel fraction. Film 10
It was cut into a cm × 10 cm square and the weight (a) was measured.
100 ml of methyl ethyl ketone at 25 ℃
It was soaked for 5 hours. The film taken out was rinsed with methyl ethyl ketone and then dried at 60 ° C. for 2 hours to obtain a weight (b).
Was measured. The gel fraction was according to the following formula. Gel fraction (%) = (a−b) / (a−c) × 100 c: weight of film only When the coating film is peeled off from the film, methyl ethyl ketone is filtered through a wire mesh of 150 mesh to The weight of the top peeled coating (dry weight) was added during the calculation.

[0030]

[Table 2]

[0031]

The biodegradable polyester adhesive of the present invention is suitable for lamination to porous or rough surface materials such as biodegradable film, biodegradable nonwoven fabric, paper and leather, and has an adhesive strength. A high and highly biodegradable laminate can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J029 AA02 AB01 AC02 AD03 AE02                       AE03 AE13 BA03 BA05 BA08                       BF09 EA01 EA02 EA03 EA05                       EG09 FC02 FC03 FC04 FC08                       JE182 KE05

Claims (2)

[Claims] 1. Containing 55 to 95 mol% of lactic acid residues and 5 to 45 mol% of caprolactone residues, the molar ratio (L / D) of L-lactic acid and D-lactic acid among the lactic acid residues is 1 The biodegradable polyester has a hydroxyl group concentration of 70 to 500 equivalents / 10 ⁶ g. 2. The biodegradable polyester according to claim 1, further comprising a polyglycerin residue.