KR19980083265A - Method for preparing biodegradable aliphatic polyester resin - Google Patents

Abstract

The present invention relates to a method for producing a biodegradable aliphatic polyester resin having a high crystallization rate, wherein sodium steric acid is 0.2 to a polybutylene succinate (PBS) having a melt flow index of 5 to 50 or a copolymer thereof as a crystallization nucleating agent. A method for producing a biodegradable aliphatic polyester resin characterized by obtaining an excellent biodegradable aliphatic polyester resin by reducing injection molding cycle and lowering the molding temperature according to the increase in crystallization temperature and crystallization rate by adding ˜1.0% by weight. will be.

Description

Method for preparing biodegradable aliphatic polyester resin

The present invention relates to a method for producing a biodegradable aliphatic polyester resin having a high crystallization rate, and more particularly, by adding a crystallization nucleating agent to a biodegradable aliphatic polyester and its copolymer, having a relatively high crystallization temperature and a crystallization rate. The present invention relates to a method for producing a biodegradable aliphatic polyester resin having no molecular weight decrease.

In general, aliphatic polyester is used for various purposes because of its excellent biodegradability, but it is useful in biodegradability that can be degraded in the natural environment when used for crop cultivation film, food packaging film, or household waste disposal bag, which is difficult to recover. It is a polymer resin. However, since the crystallization rate is relatively slow during molding as compared with other polymer materials, there is a disadvantage in that the moldability is lowered and the physical properties of the molding are lowered when used alone.

In order to solve this problem, in the case of the aromatic polyester widely used for existing fibers or films, a method of improving the crystallization rate of the melt by adding a small amount of nucleating agents has been known.

For example, in U.S. Pat.Nos. 4,440,92 and 4486561, polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and blends thereof are added to the nucleating agent of epoxidized plasticizer to reduce post-forming shrinkage, molding cycle. The moldability was improved, such as the reduction of the temperature and the decrease of the molding temperature, and the physical properties of the moldings such as flexural modulus, flexural strength, deformation temperature under load, tensile strength and solvent resistance were improved.

In addition, US Pat. No. 4,440,92 introduces a technique for improving the final crystallization rate as well as the crystallization rate during molding by adding a small amount of ionomer as a nucleating agent to a polyester blend containing PET and PET. See also the publication Plastic Engineering, 1987, Vol. 43, it can be overcome by adding a small amount of polyolefin of the molding process problem due to the slow crystallization rate of PET, in particular polyolefin resin such as polyethylene and polypropylene not only increases the crystallization rate of PET but also exhibits releasability It has been reported to improve and lower the melt viscosity.

As described above, in the case of aromatic polyester such as PET, a method of improving the crystallization rate by adding a small amount of nucleating agent is known, but in the case of aliphatic polyester which has recently been studied as a biodegradable polymer, it has been found No method is known.

The present invention focuses on the fact that aromatic and aliphatic sodium carboxylate salts are very effective as crystallization nucleating agents of aromatic polyesters. The present invention provides a method for producing a biodegradable aliphatic polyester resin capable of producing an injection molded product having a lower molecular weight while showing a relatively higher crystallization temperature and crystallization rate than zero addition. At this time, the sodium succinate salt reacts with the end groups of the polyester to form sodium ends, and these sodium ends act as nuclides that promote crystallization.

Hereinafter, the present invention will be described in more detail.

Aliphatic polyester resin with improved moldability and mechanical properties is prepared by injection molding by adding 0.2-1.0 wt% of saccharin sodium salt as crystallization nucleating agent when extruding aliphatic polyester having 5 to 50 molten flow resin or copolymers thereof. Could.

In the present invention, it is preferable to add 0.2 to 1.0% by weight of the sodium steric acid salt used as the crystallization nucleating agent, and more preferably 0.4 to 0.7% by weight. If the added amount is less than 0.2% by weight, the action as a nucleating agent is insignificant, so that an increase in the crystallization temperature or an improvement in the crystallization rate is not expected. When the addition amount is more than 1.0% by weight, the molecular weight decreases due to the nucleating agent is severe, and the mechanical properties of the molding are poor. There was a problem of deterioration.

Characterization of the aliphatic polyester according to the Examples and Comparative Examples of the present invention was carried out in the following manner.

1. Melt Flow Index (MFR)

The melt flow index was measured from the amount of resin extruded between 10 parts under a 2.16 kg load at 190 ° C. using a melt flow index meter.

2. DSC heating start temperature and DSC heating peak temperature

The differential heating calorimeter (DSC) was used to measure the exothermic starting temperature and the exothermic peak temperature of the exothermic peak that appeared during the temperature increase at 10 ° C / min after the temperature was raised to 150 ° C at a rate of 10 ° C / min. Here, the exothermic onset temperature and exothermic peak temperature are related to the crystallization temperature and speed that occur when the polymer melt is cooled. The higher the exothermic onset temperature and exothermic peak temperature, the faster the crystallization proceeds.

3. DSC melting temperature

According to KSM 3050, the melting temperature was measured by the endothermic peak appearing when the temperature was raised at a rate of 10 ℃ / min using a differential scanning calorimeter (DSC).

4. Tensile Strength and Elongation at Break

The method of ASTM D638 was used.

5. Nazid Izod Shock

Nazid specimens 1/8 inch thick were measured with an Izod impact tester according to ASTM D256.

6. Biodegradability

Incubate for at least 21 days according to ASTM G 21-70 method and the degree of mold cover on the film is 0% for 0%, 1 for less than 10%, 2 for 10-30%, 30-60 In the case of%, it was set as 3, and in the case of 60-100%, it was divided into 4 and measured.

The biodegradable aliphatic polyester prepared by adding saccharin sodium salt as a crystallization nucleating agent and copolymer resin thereof have increased crystallization rate and temperature, which reduces molding cycle during injection molding and improves moldability as the molding temperature decreases. Biodegradable resin moldings having excellent mechanical properties can be produced.

The following examples and comparative examples further illustrate the present invention in more detail, but do not limit the scope of the present invention, and% means by weight unless otherwise specified.

Example 1

0.5 wt% sodium steric acid salt was added to a polybutylene succinate (PBS) having a melt flow index (MFR) of 10.0, and a master batch was prepared by mixing sufficiently at a temperature of 150 ° C. in an extruder equipped with a dynamic mixer. The prepared master batch chip was dried in a vacuum dryer at 70 ° C. for at least 4 hours, and then injection molded in an injection molding machine using a 1/2 × 5 × 1/2 cavity (ASTM standard flex bar) under the following conditions.

● Temperature condition-1 Zone: 120 ℃, Zone 2: 125 ℃, Zone 3: 120 ℃, Zone 4: 115 ℃, Molding section: 40 ℃

● Injection pressure-150psi

● Holding Pressure -50psi

● Molding cycle (automatic cycle: sec)-delayed injection: 3.2, injection: 4.0, maintenance: 2.0 cooling: 20.0, die opening: 2.0

The crystallization characteristics of the master batch and the mechanical properties of the injection molding according to the above example were evaluated and the results are shown in Table 1.

Example 2

To the polybutylene succinate-adipate copolymer (PBS-co-BA) having a melt flow index (MFR) of 20.0, 0.4 wt% of sodium steric acid salt was added and injection molded under the same conditions as in Example 1. The crystallization properties of the master batch and the mechanical properties of the injection molding were evaluated and the results are shown in Table 2.

Comparative Examples 1 to 3

Except having changed the addition amount of the sodium succinate salt as shown in Table 1, it carried out similarly to Example 1, and the result is shown in Table 1.

Comparative Examples 4-6

Except having changed the addition amount of the sodium succinate salt as shown in Table 2, it carried out similarly to Example 2, and the result is shown in Table 2.

As shown in Table 1 and Table 2, when an appropriate amount of sodium steric acid salt acting as a crystallization nucleating agent is added, the DSC exotherm starting temperature and exothermic peak temperature are increased as in Examples 1 and 2, and as the polymer melt cools, It crystallizes at a faster rate at temperature, and the mechanical properties of the injection moldings thus formed are excellent. Therefore, by adding an appropriate amount of sodium steric acid salt to the aliphatic polyester or a copolymer thereof, it is possible to prepare a biodegradable resin having a high crystallization rate and excellent physical properties of an injection molded product.

TABLE 1

TABLE 2

As can be seen from the detailed description and the examples of the present invention, the present invention has the effect of improving the moldability and the mechanical properties of the molding by adding sodium steric acid salt, which is a crystallization nucleating agent, to aliphatic polyester, which is a biodegradable polymer. Has By using these effects, if a film for crop cultivation, a food packaging film, or a household garbage bag is difficult to recover after use, an excellent biodegradable film can be obtained in terms of physical properties.

Claims (3)

A method for producing a biodegradable aliphatic polyester resin, characterized by adding 0.2 to 1.0% by weight of sodium steric acid salt as a crystallization nucleating agent to an aliphatic polyester having a melt flow index of 5 to 50 or a copolymer thereof. The method according to claim 1, A polybutylene succinate (PBS) is used as an aliphatic polyester, The manufacturing method of the biodegradable aliphatic polyester resin characterized by the above-mentioned. The method according to claim 1, A polybutylene succinate adipate (PBS-co-BA) as the aliphatic polyester copolymer, a method for producing a biodegradable aliphatic polyester resin.