JP3018113B2 - Method for lowering molecular weight of cellulose acetate, lactone-modified cellulose acetate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graft polymer obtained by ring-opening addition polymerization of ε-caprolactone in the presence of cellulose acetate, and a method for producing the graft polymer. The present invention relates to a lactone-modified cellulose acetate having a reduced molecular weight obtained by reacting residual hydroxyl groups with ε-caprolactone after reducing the molecular weight of lactone and a method for producing the same. The lactone-modified cellulose acetate having a reduced molecular weight of the present invention is a composition useful as a resin for coating and a molding material.

[0002]

2. Description of the Related Art Cellulose acetate is one of the thermoplastic substances that is used industrially in plastics, films, fibers, semi-permeable membranes, etc., and has high transparency, colorability, printability, impact resistance, and feel. There are excellent features such as goodness. However, since thermoplasticity alone is not sufficient, it is necessary to mix and process with a plasticizer to use as plastics. At present, a plasticizer having a sufficient affinity for cellulose acetate has not been found. Therefore, there is a problem in that the plasticizer diffuses and moves after the molding process, migrates to another material in contact with the material, impairs the physical properties, and causes distortion inside the cellulose acetate molded article.

[0003]

A high molecular modifier which has a high affinity for cellulose acetate and has a higher molecular weight than the plasticizers currently used in place of the low molecular weight plasticizers currently used. Development is considered extremely useful.

It is considered that such a polymer modifier has a cellulose acetate structural portion in the molecule and also has a structural portion more flexible than the cellulose skeleton. It is thought that this can be achieved by producing a block polymer or a graft polymer.

However, when cellulose acetate produced industrially is used as a copolymerization component as it is, the degree of polymerization of the product is too high, side reactions such as cross-linking occur, and the selection range of the reaction solvent is narrow. Problematic and impractical. On the other hand, a method of obtaining a graft or block copolymer from industrially produced cellulose acetate using low molecular weight cellulose acetate having a degree of polymerization of a fraction to one-tenth of that of cellulose acetate is considered. Can be

[0006] Even with such low molecular weight cellulose acetate,
It is believed that the presence in the molecular structure of the product is sufficient to provide high affinity for high molecular weight cellulose acetate. However, production of low molecular weight cellulose acetate is usually impractical due to problems such as a large loss in the purification step.

Further, other cellulose ester derivatives such as cellulose nitrate, cellulose propionate and cellulose acetate butyrate are soluble in various solvents and have good compatibility and miscibility with plasticizers and other polymers. Many of them exhibit thermoplasticity by using a plasticizer, and are widely used in molded articles, fibers, paint resins and the like. Acids, acid anhydrides, and cellulose ester production methods
Generally, an acid halide or the like is reacted with cellulose as an esterifying agent.

On the other hand, when a cyclic ester is used as an esterifying agent, the product is a product having a free hydroxyl group, that is, a hydroxylalkyl ester of cellulose. It is expected to have physical properties and novel applications, for example, applications utilizing compatibility with hydrophilic polymers or reactivity of hydroxyl groups.

A method for producing a novel graft polymer by ring-opening polymerization of a cyclic ester in the presence of a cellulose derivative has been disclosed by the present applicant in Japanese Patent Publication No. 1-38402,
JP-A-59-86621, JP-A-60-212422
And the like, but the properties of the graft polymer are not sufficiently clarified.

[0010]

The present inventors have succeeded in industrially producing a graft polymer which is a cellulose ester having a graft chain composed of ε-caprolactone, which is not described in the prior art and is industrially useful. Clarified the properties of the graft polymer. Moreover, the degree of polymerization of the above-mentioned graft polymer does not become too high even when industrially produced high molecular weight cellulose acetate is used as a raw material. Furthermore, according to the production method of the present invention, side reactions such as cross-linking do not occur, and it is tough, rich in flexibility, and has a primary hydroxyl group that is a reactive group, and is useful as a resin for paint and a molding material. The present inventors have found that lactone-modified cellulose acetate can be produced, and have completed the present invention.

[0011]

That is, the present invention provides:
"It is characterized in that 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more is heat-treated in the presence of 50 to 90 parts by weight of ε-caprolactone. Method for lowering the molecular weight of cellulose acetate "and

[0012] By heating 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more in the presence of 50 to 90 parts by weight of ε-caprolactone. After performing the molecular weight reduction of the corresponding cellulose acetate, a ring-opening polymerization catalyst is added, and a low molecular weight lactone-modified cellulose acetate obtained by ring-opening addition polymerization of ε-caprolactone to the remaining hydroxyl group '' and

[0013] By heating 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more in the presence of 50 to 90 parts by weight of ε-caprolactone. After performing the molecular weight reduction of the corresponding cellulose acetate, a method for producing a low molecular weight lactone-modified cellulose acetate, characterized by adding a ring-opening polymerization catalyst and subjecting the remaining hydroxyl groups to ring-opening addition polymerization of ε-caprolactone. ".

It is essential that the cellulose acetate used in the present invention has a degree of acetyl substitution of 1.7 to 2.9 and a number average polymerization degree of 50 or more. Currently, cellulose acetate used industrially has a degree of polymerization of 100.
Those having a polymerization degree in the range of about to 400 and a polymerization degree of 50 or less are not industrially produced. Those having an acetyl substitution degree of 1.7 or less are not preferred because they have poor solubility in ε-caprolactone and poor ring-opening addition reactivity to free hydroxyl groups of cellulose acetate.

On the other hand, those having an acetyl substitution degree of 2.9 or more are not preferred because the absolute number of free hydroxyl groups of cellulose acetate is reduced and the ring-opening addition reactivity of ε-caprolactone is inferior. The amount of cellulose acetate used is 10 to 50 parts by weight based on 50 to 90 parts by weight of ε-caprolactone.

When the amount of cellulose acetate is 10 parts by weight or less, the proportion of cellulose acetate in the system becomes small, and the ring-opening addition amount of ε-caprolactone to cellulose acetate relatively increases. Cannot exhibit the performance possessed by In this case, it is considered that the ring-opening addition reaction of ε-caprolactone may be stopped halfway, and the reaction product may be taken out of the reaction system. However, a large amount of unreacted ε-caprolactone also exists in the reaction system. Not.

On the other hand, if the amount of cellulose acetate is more than 50 parts by weight, the solubility of cellulose acetate in ε-caprolactone becomes poor, and the viscosity of the reaction system increases, which is not practical. The heat treatment for a certain period described in the present invention specifically means that the heat treatment is performed at a temperature of 180 ° C. or more and 230 ° C. or less for at least one time.
Indicates that heat treatment is performed for 0 minutes or more. When the processing temperature is 18
At 0 ° C. or lower, the expected low molecular weight of cellulose acetate cannot be achieved. At 230 ° C. or higher, decomposition of cellulose acetate occurs at an accelerated rate, and the reaction system becomes violently colored, which is not practical.

If the treatment time is 10 minutes or less, the expected low molecular weight of cellulose acetate cannot be achieved. The ring-opening polymerization catalyst used in the present invention includes alkali metals such as sodium and potassium and derivatives thereof, tertiary amines such as pyridine, alkyl aluminum and derivatives thereof represented by triethyl aluminum, and alkoxy represented by tetrabutyl titanate. Titanium compound, tin octylate,
An organic metal compound such as dibutyltin laurate and a metal halide such as tin chloride may be used.

The ring-opening polymerization catalyst for these cyclic esters is
Seisho, Takeo Saegusa, “Course polymerization reaction theory (7), Ring-opening polymerization (II)”, published by Kagaku Doujin (1973), p. 107-1
31. The polymerization temperature for obtaining the graft polymer is a temperature usually applied to ring-opening polymerization of a cyclic ester, and preferably, the reaction is performed at a temperature of 120 ° C to 210 ° C under a dry nitrogen atmosphere.

The reaction time may be generally about 0.5 to 20 hours. Further, it is desirable that the raw materials, nitrogen, reactive groups, and the like used in obtaining the graft polymer of the present invention are sufficiently removed from water and dried. The reaction product thus obtained may partially contain a graft polymer, an unreacted ε-caprolactone and a homopolymer of ε-caprolactone. This is performed using a good solvent and a poor solvent according to the solvent fractionation method.

When the graft polymerization of the present invention is used as a coating resin, it has good compatibility with other thermoplastic resins and a coating film having excellent performance can be obtained. Also, when used as a molding material, it has a flexibility that cannot be exhibited only by cellulose ester, and is therefore used as a material that does not require a plasticizer such as a phthalate ester.

The primary hydroxyl group present at the end of the graft chain of the graft polymer has excellent reactivity and can be used for the reaction with an isocyanate group, an acid halide group and an epoxy group.
Therefore, it is also possible to further react the graft polymer to chemically modify or reticulate it. It is also useful as a fiber, separation membrane, film and clothing material. Next, the graft polymer of the present invention will be described in more detail in Examples.

[0023]

Example 1 In a sufficiently dried reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, under a dry atmosphere, fully dried cellulose acetate (manufactured by Daicel Chemical Industries, Ltd.). -3, degree of acetylation 55.6%, degree of substitution 2.
46, an average degree of polymerization of about 100, and 337.2 g of a glucose unit having a molecular weight of 263.08 were charged in the presence of 1462.8 g of ε-caprolactone (molecular weight of 114.15).

The mixture was gradually heated to 100 ° C. with stirring, and it was confirmed that the mixture became substantially uniform. After that, the temperature was increased to 18
The temperature was raised to 0 ° C. and kept at this temperature for 1 hour. Solution 10
After cooling to 0 ° C., tetrabutyl titanate ((C4H
9) 0.018 g of 4OTi) was added, and the temperature was raised again and kept at 160 ° C. for 1.5 hours. Thereafter, the reaction solution was cooled to room temperature to terminate the reaction, and a crude polymerization solution was obtained.

1000 g of the crude polymer solution is slowly dropped into a large excess of methanol (8 times the amount of the crude polymer solution) with stirring. The precipitated polymer is separated by filtration and washed again with a large excess of methanol under stirring. After repeating the washing operation twice, the mixture was separated by filtration and dried in an oven at 70 ° C. for 1 hour. According to C13-NMR analysis of the fractionated graft polymer, the amount of ε-caprolactone added to one glucose unit was 0.928 m
ol, and the melting point was 222 to 226 ° C.

Acetone was added to the graft polymer to add
When a 0% solution was prepared, the hue was 80 APHA, and the viscosity of the solution was 26.3 cp (25 ° C.). Next, the solubility of the graft polymer in a solvent and the compatibility with other resins were measured. The results are shown in Tables 1 and 2 together with Examples 2, 3 and Comparative Examples 1 to 4 described below.

Each symbol representing the criterion in Table 2 means the following. ◎: Completely compatible to form a transparent film. : Completely compatible with each other to form a transparent film, but in winter and the like, a few crystals are precipitated in the film after several days, and slightly white spots are generated. Δ: It becomes cloudy due to crystal precipitation, but dissolves when heated to 50 to 70 ° C. and becomes completely compatible. However, it becomes cloudy immediately upon cooling. ×: No compatibility

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

Example 2 After adding the catalyst, the temperature was raised again to
The same operation as in Example 1 was performed except that the temperature was maintained at 60 ° C. for 3 hours.

[0031]

Example 3 After adding the catalyst, the temperature was raised again to
The same operation as in Example 1 was performed except that the temperature was maintained at 60 ° C. for 5 hours.

[0032]

[Comparative Example 1] Cellulose acetate used as a raw material when synthesizing a graft polymer (manufactured by Daicel Chemical Industries, Ltd.)
3, the degree of acetylation is 55.6%, the degree of substitution is 2.46, the average degree of polymerization is about 100, the hue is 40 when a 20% solution is prepared by adding acetone to a molecular weight of 263.08 per glucose unit).
APHA, solution viscosity is 1579 cp (25 ° C.)
Met. In addition, the solubility of the cellulose acetate in the solvent and the compatibility with other resins were measured.

[0033]

COMPARATIVE EXAMPLE 2 In a sufficiently dried reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, under a dry atmosphere, fully dried cellulose acetate (manufactured by Daicel Chemical Industries, Ltd.). -3, degree of acetylation 55.6%, degree of substitution 2.
46, an average degree of polymerization of about 100, and 337.2 g of a glucose unit having a molecular weight of 263.08 were charged in the presence of 1462.8 g of ε-caprolactone (molecular weight of 114.15). The mixture was gradually heated to 100 ° C. with stirring, and it was confirmed that the mixture became substantially uniform. Thereafter, 0.018 g of tetrabutyl titanate ((C4H9) 4OTi) was added,
The temperature was raised and held at 160 ° C. for 3 hours. Thereafter, the reaction solution was cooled to room temperature to terminate the reaction, and a crude polymerization solution was obtained.
Thereafter, the same operation as in Example 1 was performed, and the properties of the obtained graft polymer were observed.

[0034]

Comparative Example 3 After adding the catalyst, the temperature was increased to 160
The same operation as in Comparative Example 2 was performed except that the temperature was kept at 6 ° C. for 6 hours.

[0035]

Comparative Example 4 After adding the catalyst, the temperature was increased to 160
The same operation as in Comparative Example 3 was performed except that the temperature was kept at 7.2 ° C. for 7.2 hours.

[0036]

Industrial Applicability According to the present invention, an industrially useful graft polymer which is a cellulose ester having a graft chain of ε-caprolactone, which has not been described in the literature, has been industrially produced, and the graft weight has been further improved. The properties of the coalescence were clarified, and the graft polymer had better performance in solubility and compatibility due to its low molecular weight. In addition, even if high-molecular weight cellulose acetate is used as a raw material, the degree of polymerization of the product is too high, side reactions such as cross-linking do not occur, and it has a primary hydroxyl group that is tough, flexible and reactive. It was found to be useful as a resin for paint and a molding material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI // C09D 101/12 C09D 101/12

Claims (3)

(57) [Claims] 1. Heat-treating 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more in the presence of 50 to 90 parts by weight of ε-caprolactone. A method for reducing the molecular weight of cellulose acetate. 2. Heat treatment of 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more in the presence of 50 to 90 parts by weight of ε-caprolactone. A low molecular weight lactone-modified cellulose acetate obtained by adding a ring-opening polymerization catalyst and subjecting the remaining hydroxyl group to ring-opening addition polymerization of ε-caprolactone after carrying out the molecular weight reduction of the corresponding cellulose acetate. 3. Heat-treating 10 to 50 parts by weight of cellulose acetate having an acetyl substitution degree of 1.7 to 2.9 and a number average polymerization degree of 50 or more in the presence of 50 to 90 parts by weight of ε-caprolactone. Production of low molecular weight lactone-modified cellulose acetate, characterized by adding a ring-opening polymerization catalyst after carrying out the molecular weight reduction of the corresponding cellulose acetate by the above, and subjecting the remaining hydroxyl groups to ring-opening addition polymerization of ε-caprolactone. Method.