JP2003238669A - Thermoplastic cellulose acetate and fiber made thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic cellulose acetate having an aliphatic polyester graft side chain which is excellent in the moldability and mechanical properties and a fiber made of it which is excellent in the ability of melt spinning and the strength elongation properties. <P>SOLUTION: The thermoplastic cellulose acetate has the aliphatic polyester side chain with a specified degree of acetyl substitution, a specified molecular weight of the graft side chain and a specified melt viscosity, and the fiber is made of it. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic cellulose acetate having an aliphatic polyester graft side chain and a fiber comprising the same.

[0002]

2. Description of the Related Art Cellulosic materials such as cellulose and cellulose derivatives such as cellulose esters and cellulose ethers are currently used as the most mass-produced biomass materials on earth and as biodegradable materials in the environment. It is getting a lot of attention. Among the cellulose derivatives, the one with the lowest price and the largest industrial production is cellulose acetate, which is used in a wide range of fields such as fibers, plastics, filters and films.

Cellulose acetate has insufficient thermoplasticity, and if it is heated and melted as it is, it has a problem that it is decomposed or colored before being softened. Therefore, a suitable external plasticizer must be used for thermoplastic processing. Currently, low molecular weight plasticizers such as triacetin and polycaprolactone oligomer are industrially used, but these have problems such as bleed-out during thermoplastic molding and clouding of the surface of the molded product.

In contrast to this method, an internal plasticizing method utilizing residual hydroxyl groups of cellulose acetate is disclosed in Japanese Patent Laid-Open No. 58-58
225101, JP-A-59-86621,
JP-A-7-179662 and JP-A-11-2558.
No. 01, etc., cellulose acetate mainly having ε-caprolactone as a graft chain and a method for producing the same are known. Although these polymers have no bleed-out concern, their use is limited due to the low melting point of the polymer on the graft side chain, clouding of the molded product due to crystallization of the graft side chain occurs, and when used as a fiber Had problems such as a slimy feeling.

On the other hand, a method for producing a cellulose derivative using lactide, which is a dimer of lactic acid, as a monomer to be grafted is disclosed in JP-A-6-287279. Since the polylactic acid itself having a graft side chain is a polymer having high thermal stability, its application range is widened, but since the crystallinity is high, the resulting polymer has a problem of high brittleness and poor mechanical properties. In addition, since lactide is used in an amount 9 times or more the weight of cellulose acetate, the properties of the side chain polylactic acid become remarkable, and the properties peculiar to cellulose acetate such as dry texture, moderate hygroscopicity, and good There is a problem that dimensional stability and the like are lost.

[0006]

The object of the present invention is to solve the above-mentioned problems and to have a specific acetyl substitution degree and a graft side chain of a specific molecular weight, excellent moldability and mechanical properties,
It is to provide a thermoplastic cellulose acetate that retains the properties of cellulose acetate. Further, it is to provide a fiber made of this thermoplastic cellulose acetate, which has excellent melt spinnability and excellent strength and elongation characteristics.

[0007]

The above-mentioned object of the present invention is to provide a thermoplastic cellulose having an acetyl substitution degree of 2.5 to 3.0 and having an aliphatic polyester graft side chain containing lactic acid as a main repeating unit. The average molecular weight of the aliphatic polyester, which is an acetate and is introduced into the side chain, is 1,000 to 10,000, 220 ° C, 1,000s
ec ⁻¹ has a melt viscosity of 50 to 300 Pa.s. It can be solved by a thermoplastic cellulose acetate characterized by being sec.

Another object of the present invention can be solved by a fiber made of thermoplastic cellulose acetate having the above characteristics. In this case, the strength is 0.5 to 2.0c
N / dtex and an elongation of 5 to 50% can be suitably adopted.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention will be described in detail below. The degree of acetyl substitution of cellulose acetate in the present invention is 2.5 to 3.0 per glucose unit. The thermoplastic cellulose acetate having an aliphatic polyester graft side chain having an acetyl substitution degree in this range has a remarkable plasticizing effect, and the brittleness of the obtained polymer does not pose a problem. If the degree of acetyl substitution is less than 2.5, hydrogen bonding due to residual hydroxyl groups in the cellulose acetate causes a small plasticizing effect even when an aliphatic polyester is grafted to the side chain, resulting in poor moldability, and further resulting molding The high brittleness of the material is a big problem. In addition, the miscibility with lactide which is a graft side chain is poor. The degree of acetyl substitution is preferably 2.7 to 3.0, and most preferably 2.7 to 2.9.

The average degree of polymerization of the cellulose acetate in the present invention is not particularly limited, but in order to obtain a thermoplastic cellulose acetate having an aliphatic polyester side chain which is excellent in thermal stability and mechanical properties, it is preferable to use 50 or more. It is preferably used, and more preferably 100 or more.

The aliphatic polyester graft side chain in the present invention is a polymer mainly containing lactic acid as a repeating unit. Polylactic acid containing lactic acid as a repeating unit is suitable because it has particularly high thermal stability among aliphatic polyesters. Lactide used in the present invention is a compound obtained by cyclic dimerization of lactic acid. Lactide is an L consisting of two L-lactic acids
-Lactide, D-lactide consisting of two D-lactic acids, L
There is MESO-lactide consisting of lactic acid and D-lactic acid. In the present invention, these three kinds of lactides can be arbitrarily combined.

The molecular weight of the aliphatic polyester graft side chain in the present invention is 1,000 to 10,000. When the molecular weight is in the range of 1,000 to 10,000, the plasticizing effect is increased, the strength is improved, and the molding temperature can be lowered. On the other hand, if the molecular weight is less than 1000, the plasticity effect is small because the rigidity of the cellulose chain is emphasized,
Further, the obtained polymer has a high melt viscosity and has a problem of poor moldability, and the mechanical properties are also highly brittle. On the other hand, when it is more than 10,000, there is a problem that the characteristics of the side chain aliphatic polyester are emphasized and the characteristics peculiar to cellulose acetate disappear, and the melt viscosity becomes high, resulting in poor moldability. From the viewpoint of good flow properties, mechanical properties and moldability, the molecular weight of the aliphatic polyester side chain is more preferably 2000 to 9000, most preferably 30.
It is from 00 to 8000.

In order to obtain the thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention, a method of carrying out ring-opening graft polymerization of cellulose acetate with lactide as a monomer can be exemplified, but other known methods can be used. Good.

In this case, the graft reaction may be a reaction in an organic solvent capable of dissolving the cellulose acetate and the monomer used,
It may be a reaction using a batch kneader capable of heating and stirring while applying a shearing force, or a reaction using a uniaxial or biaxial extruder. In each case, it is important that the raw materials used in the reaction are highly dried to remove water. When a batch type kneader is used, it is preferable to replace the inside with a dry inert gas such as nitrogen. Also in the case of using an extruder, it is preferable to replace the inside with an inert gas dried with nitrogen or the like, or to bring the inside into a decompressed state with a decompressor.

When carrying out the ring-opening graft reaction, it is desirable to use a known ring-opening polymerization catalyst. Examples of the catalyst that can be used include metals such as tin, zinc, titanium, bismuth, zirconium, germanium, antimony, sodium, potassium and aluminum, and derivatives thereof, and particularly, for the derivatives, metal organic compounds, carbonates, oxides, halogens. Compounds are preferred. Specifically, tin octoate, tin chloride, zinc chloride, alkoxy titanium, germanium oxide, zirconium oxide, antimony trioxide, alkylaluminum and the like can be exemplified.

In the production of the thermoplastic cellulose acetate having an aliphatic polyester graft side chain according to the present invention, the cellulose acetate is easily dissolved in lactide, and in order for the reaction to proceed easily and uniformly, the cellulose acetate / lactide used The weight ratio is preferably 2 or more, more preferably 3 or more.

When the thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention is polymerized, ring-opening polymerization of lactides also progresses as a side reaction to produce ungrafted polylactic acid. Homopolylactic acid produced as a by-product can function as an external plasticizer, and therefore it is not always necessary to completely remove it by purification.

The thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention is 22
Melt viscosity at 0 ° C and 1000 sec-1 is 50 to 3
It is 00 Pa · sec. When the melt viscosity at 220 ° C. and 1000 sec-1 is 50 to 300 Pa · sec, for example, in the case of fiberizing, the solidification after spinning is sufficiently advanced, and the fibers do not stick to each other even when converged. . Further, in this case, since the back pressure of the die is sufficiently obtained, there is an advantage that the dispersibility becomes good and the uniformity of the fineness is secured. Furthermore, the spinnability of the spun yarn is good, sufficient orientation is obtained, and a fiber with excellent mechanical properties is obtained. In addition, no trouble will occur due to an abnormal increase in piping pressure. 220 in terms of good flowability and mechanical properties
Melt viscosity at 1000 ° C for 1000 sec-1 is 70-250
Pa · sec is more preferable, and it is 80 to 200.
Most preferably, it is Pa · sec.

The thermoplastic cellulose acetate having an aliphatic polyester graft side chain is not limited to fibers and can be used in various fields such as sheets, films, pipes, toys, tools, tableware and the like. .

The thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention is a matting agent, a deodorant, a flame retardant, a yarn friction reducing agent, an antioxidant, a coloring pigment, an electrostatic agent, an antibacterial agent, etc. As the inorganic fine particles or the organic compound, it is possible to add them.

A known plasticizer can be added to the thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention, if necessary. When a large amount of a plasticizer is contained, there may be a problem of smoke emission during melt spinning due to evaporation of the plasticizer, and a problem of slimy feeling due to bleed-out of the plasticizer on the fiber surface. From this fact, particularly when a relatively low molecular weight plasticizer having a molecular weight of less than 1000 is used, cellulose acetate having an aliphatic polyester graft side chain 10
It is preferable not to exceed 5 parts by weight with respect to 0 parts by weight,
More preferably, it does not exceed 2 parts by weight. Specific examples of plasticizers that can be used include relatively low molecular weight plasticizers such as dimethyl phthalate, diethyl phthalate, dihexyl phthalate, dioctyl phthalate, dimethoxy ethyl phthalate, ethyl phthalyl ethyl glucolate, butyl phthalate. Phthalates such as rubutyl glycolate, aromatic polyvalent carboxylic esters such as tetraoctylpyromellitate and trioctyl trimellitate, dibutyl adipate, dioctyl adipate, dibutyl sebacate, dioctyl sebacate, diethyl azelate , Dibutyl azelate, dioctyl azelate and other aliphatic polycarboxylic acid esters, glycerin triacetate, diglycerin tetraacetate and other polyhydric alcohol lower fatty acid esters, trie Ruhosufeto, may be mentioned tributyl phosphate, tributoxyethyl phosphate, phosphoric acid esters such as tricresyl phosphate and the like. When a relatively high molecular weight plasticizer having a molecular weight of 1000 or more is used, it is 20 per 100 parts by weight of cellulose acetate having an aliphatic polyester graft side chain.
It is preferably not more than 10 parts by weight, more preferably not more than 10 parts by weight. Examples of the plasticizer in this case include aliphatic adipates such as polyethylene adipate, polybutylene adipate, polyethylene succinate, and polybutylene succinate, and oxycarboxylic acids such as polylactic acid and polyglycolic acid. And aliphatic polymers such as polycaprolactone, polypropiolactone and polyvalerolactone, and vinyl polymers such as polyvinylpyrrolidone. These plasticizers can be used alone or in combination.

The thermoplastic cellulose acetate having an aliphatic polyester graft side chain according to the present invention can be made into fibers by melt spinning, and the obtained fibers show good mechanical properties. The strength of the fiber made of thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention has a strength of 0.5 to 4.0 cN / dte.
It is preferably x. Strength is 0.5 cN / dtex
The above values are preferable because the passability in high-order processing steps such as weaving and knitting is good, and the strength of the final product is not insufficient. Further, it is practically difficult to obtain a high-strength fiber exceeding 4.0 cN / dtex, and when a treatment for forcibly increasing the molecular orientation by an operation such as draft improvement or stretching is performed to increase the strength, The residual elongation may be too low. From the viewpoint of good strength characteristics, the strength is more preferably 0.7 cN / dtex or more, and most preferably 1.0 cN / dtex or more.

The elongation of the fiber made of thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention is preferably 5 to 50%. When the elongation is 5% or more, yarn breakage does not occur frequently in higher-order processing steps such as weaving and knitting. Further, fibers having an elongation of 50% or less do not deform under low stress and do not cause dyeing defects in the final product due to weft shrinkage during weaving, which is preferable. The good elongation is more preferably 15 to 45%, and is 20
Most preferably, it is -40%.

The single yarn fineness of the fiber made of thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention is preferably 0.5 to 100 dtex. If the single yarn fineness is 0.5 dtex or more,
Fibers can be obtained with good spinnability by the direct melt spinning method. If the single yarn fineness is 100 dtex or less,
It can also be applied to clothing fabrics and the like that require softness without the bending rigidity of the fiber structure becoming too large. The single yarn fineness is preferably 0.7 to 50 dtex, and most preferably 1 to 25 dtex.

The fiber cross-sectional shape of the fiber made of thermoplastic cellulose acetate having an aliphatic polyester graft side chain in the present invention is not particularly limited, and may be a substantially perfect circular cross section, or a multi-lobed structure. A modified cross section such as a shape, a flat shape, an elliptical shape, a W shape, an S shape, an X shape, an H shape, a C shape, a square shape, a double girder shape, or a hollow shape may be used. Further, it may be a composite fiber such as a core-sheath composite, an eccentric core-sheath composite, a side-by-side type composite, and a mixed fiber of different fineness.

The fibers of the thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention can be used as filaments for clothing, staples for clothing, filaments for industry, staples for industry, and fibers for non-woven fabric. It can also be preferably adopted.

In the melt spinning method used in the present invention, thermoplastic cellulose acetate having an aliphatic polyester graft side chain is melted by heating in a known melt extrusion spinning machine, then extruded from a spinneret, spun, and stretched if necessary. It is possible to adopt a method of rolling up. At this time, the spinning temperature is preferably 180 to 250 ° C., more preferably 190.
~ 240 ° C. When the spinning temperature is 180 ° C. or higher, the melt viscosity is lowered and the melt spinnability is improved, which is preferable. Further, when the temperature is 250 ° C. or lower, thermal decomposition of the composition is suppressed, which is preferable.

[0028]

The present invention will be described in more detail with reference to the following examples. Each characteristic value in the examples was determined by the following method.

A. Acetyl substitution degree It was calculated using the following formula.

Degree of acetyl substitution = (degree of acetylation × 3.86) /
(142.9-Acetification degree) The degree of acetylation in the formula (means the amount of bound acetic acid, and refers to the weight percentage of bound acetic acid per unit weight of cellulose, and is a method for measuring the degree of acetylation of ASTM: D-817-91. Can be measured according to the above). Accurately weigh 1.9 g of dried cellulose acetate,
After dissolving in 150 ml of a mixed solvent of acetone and dimethylsulfoxide (volume ratio 4: 1), 30 ml of 1N-sodium hydroxide aqueous solution is added and saponification is carried out at 25 ° C. for 2 hours. Phenolphthalein was added as an indicator, 1N
Titrate excess sodium hydroxide with sulfuric acid (concentration factor: F). In addition, a blank test is performed by the same method as above, and the acetylation degree is calculated by the following formula.

Degree of acetylation (%) = [6.5 × (B−A) × F] / W In the formula, A is the titer of 1N-sulfuric acid in the sample (ml), B is 1N− in the blank test. Titrate of sulfuric acid (ml), F is 1N
-Sulfuric acid factor, W indicates the weight (g) of the sample.

B. Average Degree of Polymerization The average degree of polymerization is the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of the Textile Society, Vol. 18, No. 1, pp. 105-120,
1962). Specifically, cellulose acetate is dissolved in a mixed solution of methylene chloride / methanol = 9/1 (weight ratio) to give a predetermined concentration c (2.0
0 g / L) solution is prepared. This solution is poured into an Ostwald viscometer, and the time t (second) at which the solution passes between the marking lines of the viscometer is measured at 25 ° C. On the other hand, also for the mixed solvent alone, the passage time t0 (second) was measured in the same manner as above, and the average degree of polymerization was calculated according to the following formula.

Ηrel = t / t0 [η] = (lnηrel) / c DP = [η] / (6 × 10 ⁻⁴ ) In the formula, t (sec) is the transit time of the solution and t0 (sec) is the solvent. Passage time, c (g / L) is the concentration of cellulose acetate in the solution, ηrel is the relative viscosity, [η] is the intrinsic viscosity, and DP is the average degree of polymerization.

C. It was calculated by multiplying the value obtained by dividing the average molecular weight molar substitution degree of the grafted side chain by the number of residual hydroxyl groups (that is, the number obtained by subtracting the acetyl substitution degree from 3 hydroxyl groups per glucose) and the molecular weight of lactide. The method for calculating the degree of molar substitution is 1H-NMR (JNM-E manufactured by JEOL Ltd.).
X-270; solvent: deuterated chloroform). 1.
The signal between 8 and 2.2 ppm is assigned to the acetylmethyl group of cellulose acetate, and the signal between 1.3 and 1.7 ppm is assigned to the methyl group of lactide. The area of each signal was substituted into the following equation to calculate the degree of molar substitution. Molar degree of substitution = {(signal area derived from methyl proton of lactide / 6) / (signal area derived from acetylmethyl proton of cellulose acetate / 3)} × degree of acetyl substitution D.M. Using a Capillograph manufactured by Toyo Seiki Co., Ltd., 20 g of a measurement sample, which had been dried in a vacuum at a melt viscosity of 60 ° C. for 24 hours and dried, was measured at a temperature of 220 ° C. and a die size of 1 mmφ × 10 m.
The melt viscosity was measured under the condition of mL, and the relational expression of the shear rate dependence of the melt viscosity was obtained.
The melt viscosity at c ^-1 was calculated, and the melt viscosity (Pa
・ Sec).

E. Strength and Elongation Tensilon UCT-100 manufactured by Orientec Co., Ltd. was used to perform a tensile test under the conditions of a sample length of 20 cm and a tensile speed of 20 mm / min, and the stress at the point of maximum load was measured as the fiber strength (cN / dtex). And The elongation at break was taken as the elongation (%) of the fiber.

F. When performing melt-spinning, those that can be stably made without yarn breakage are ○, those that show slight single yarn breaks are △, those that are not stable at all and cannot be made. And

G. Texture A 27-gauge circular knitting was made using the obtained fiber, and the texture was evaluated by a sensory test. A sample having a dry feeling was marked with O, a sample having a slight dry feeling was marked with Δ, a sample having no dry feeling and a sample having a slimy feeling were marked with X.

Example 1 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average degree of polymerization: 180) completely dried by vacuum drying at 60 ° C. for 24 hours and vacuum drying at 60 ° C. for 24 hours. Then, 400 parts by weight of L-lactide (manufactured by Purak Co., Ltd.) which was completely dried by the above method was placed in a four-neck flask under a nitrogen atmosphere with a Dimroth condenser and a thermocouple, and the flask was immersed in an oil bath. 140 ℃, 6
The system was dissolved by stirring for 0 minutes. Then, as a ring-opening polymerization catalyst, 0.5 part by weight of tin octoate was added and reacted for 60 minutes. After completion of the reaction, the flask was taken out from the oil bath, cooled, and chloroform was added to completely dissolve the system. The chloroform solution of the reaction product was added to a large excess of methanol to precipitate the reaction product, and suction filtration and drying were performed to obtain a flaky reaction product.

The polymer obtained had a graft side chain molecular weight of 5040 and a melt viscosity of 145 Pa · sec, indicating good heat fluidity.

This polymer was dried in vacuum at 60 ° C. for 24 hours under an absolute dry condition and then used in a single-screw melt spinning machine.
Melt at a melter temperature of 220 ° C and a pack part temperature of 220 ° C, and 0.23 mm under a discharge rate of 7.2 g / min.
It was spun from a die having 24 holes of φ-0.30 mmL. No smoke was observed from the spun yarn, and the discharged state was stable. The spun yarn is cooled by a chimney wind at 25 ° C., an oil agent is applied, and the yarn is converged.
1st godet roller that rotates in minutes
The winding tension is 0.1 cN / dtex through the second godet roller that rotates at the same speed as the godet roller.
It was wound with a winder that rotates at a speed of. The spinnability during melt spinning was good and no yarn breakage was observed. The obtained fiber had a single yarn fineness of 3.0 dtex, a strength of 1.1 cN / dtex, and an elongation of 18%.

A tube knitting machine (Maruzen Sangyo Co., Ltd.)
An attempt was made to produce a knitted fabric with a cylinder knitting machine MR1 type, 27 gauge). As a result, a knitted fabric having a good knitting property and having a soft and dry texture was obtained.

Example 2 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average degree of polymerization: 180) and 600 parts of L-lactide.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1 except that the weight part was used. The polymer obtained has a graft side chain molecular weight of 6700 and a melt viscosity of 100 Pa.
・ It was sec. The spinnability during melt spinning is good,
No thread break was observed. The obtained fiber has a single yarn fineness of 3.0 dtex and a strength of 1.2 cN / det.
x, the elongation was 20%. Further, when the production of the knitted fabric was tried, a knitted fabric having a soft and dry texture was obtained.

Example 3 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.9, average polymerization degree: 160) and 800 parts of L-lactide.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1 except that the weight part was used. The polymer obtained has a graft side chain molecular weight of 9800 and a melt viscosity of 180 Pa.
・ It was sec. The spinnability during melt spinning is good,
No thread break was observed. The obtained fiber has a single yarn fineness of 3.0 dtex and a strength of 1.4 cN / det.
x, the elongation was 21%. Further, when the production of the knitted fabric was tried, a knitted fabric having a soft and dry texture was obtained.

Example 4 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.7, average degree of polymerization: 180) and 300 parts of D-lactide.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1 except that the weight part was used. The obtained polymer has a graft side chain molecular weight of 2500 and a melt viscosity of 205 Pa.
・ It was sec. The spinnability during melt spinning is good,
No thread break was observed. The obtained fiber has a single yarn fineness of 3.0 dtex and a strength of 0.8 cN / det.
x, the elongation was 10%. Further, when the production of the knitted fabric was tried, a knitted fabric having a soft and dry texture was obtained.

Example 5 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average degree of polymerization: 180) and 4 parts of D, L-lactide.
Grafting reaction and melt spinning were performed in the same manner as in Example 1 except that the amount was set to 00 parts by weight. The polymer obtained had a grafted side chain molecular weight of 4460 and a melt viscosity of 135.
It was Pa · sec. The spinnability during melt spinning was good and no yarn breakage was observed. The obtained fiber has a single yarn fineness of 3.0 dtex and a strength of 1.1 cN / de.
The tx and the elongation were 25%. Further, when the production of the knitted fabric was tried, a knitted fabric having a soft and dry texture was obtained.

Comparative Example 1 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.4, average degree of polymerization: 180) and 600 parts of L-lactide.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1 except that the weight part was used. The obtained polymer has a graft side chain molecular weight of 1440 and a melt viscosity of 55 Pa.
It was sec. When melt spinning was performed, single yarn breakage and fluff frequently occurred. The obtained fiber had a single yarn fineness of 3.0 dtex. In addition, the strength is 0.7 cN /
The dtex and the elongation were very low at 5.5%, and the spinnability was poor. When the knitted fabric was produced using a tube knitting machine, tightness frequently occurred due to too low elongation.

Comparative Example 2 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average polymerization degree: 180) and 200 parts of L-lactide.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1 except that the weight part was used. The polymer obtained has a graft side chain molecular weight of 330 and a melt viscosity of 1115 Pa.
・ It was sec. Melt spinning was not possible due to its very high viscosity.

Comparative Example 3 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average degree of polymerization: 180) and 200 parts of L-lactide.
Grafting reaction and melt spinning were performed in the same manner as in Example 1 except that the amount was 0 part by weight. The obtained polymer has a graft side chain molecular weight of 22,000 and a melt viscosity of 250.
It was Pa · sec. At the time of melt spinning, some single yarn breakage was observed. Further, due to the thermal decomposition of the polylactic acid, which is the side chain of the graft, smoke was emitted and lactide was precipitated immediately below the base. The single yarn fineness of the obtained fiber is 3.0 dt.
ex, strength is 1.1 cN / dtex, and elongation is 19
%Met. When we tried to make a knitted fabric, the knitted fabric did not feel dry.

Comparative Example 4 100 parts by weight of cellulose acetate (acetyl substitution degree: 2.8, average degree of polymerization: 180) and 600 parts by weight of ε-caprolactone (manufactured by Wako Pure Chemical Industries, Ltd.) were used.
Grafting reaction and melt spinning were carried out in the same manner as in Example 1. The molecular weight of the grafted side chain of the obtained polymer is 100.
It was 0 and the melt viscosity was 50 Pa · sec. Although the spinnability was good, the single fiber fineness of the obtained fiber was 3.0 dtex. Also, the strength is 0.2 cN / d
The value was as low as tex, and the elongation was 80%, which was too high. Further, when an attempt was made to produce a knitted fabric, softening due to friction heating was observed, and knitting property was poor. The resulting knitted fabric had a strong slimy feel and was unsuitable for clothing.

[0050]

[Table 1]

[0051]

INDUSTRIAL APPLICABILITY Since the thermoplastic cellulose acetate having an aliphatic polyester graft side chain of the present invention has a specific degree of acetyl substitution and a specific molecular weight of the graft side chain, it has excellent melt moldability and mechanical properties. It becomes possible to provide a molded product. The obtained thermoplastic cellulose acetate having an aliphatic polyester graft side chain is used in fields utilizing biodegradability, that is, agricultural materials, forestry materials, fishery materials, civil engineering materials, sanitary materials, daily necessities, clothing fibers, industrial use. It can be suitably used as a fiber, a non-woven fabric or the like.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J029 AA02 AB01 AC05 AD01 AD10                       AE02 EH03 JE012 KA02                       KB16                 4L035 AA02 BB40 EE01 EE08 EE20                       FF00 FF02 FF04 FF05 FF10                       GG06 HH01 HH10

Claims (3)

[Claims] 1. A degree of acetyl substitution of 2.5 to 3.0,
A thermoplastic cellulose acetate having an aliphatic polyester grafted side chain containing lactic acid as a main repeating unit, wherein the average molecular weight of the aliphatic polyester introduced into the side chain is 1,000 to 10,000, and 220 ° C, 10 ° C.
The melt viscosity at 00 sec ^-1 is 50 to 300 Pa.s. s
A thermoplastic cellulose acetate characterized by being ec. 2. A fiber comprising the thermoplastic cellulose acetate according to claim 1. 3. A fiber made of thermoplastic cellulose acetate according to claim 2, which has a strength of 0.5 to 4.0 cN / dtex and an elongation of 5 to 50%.