KR20160029310A - 3d printer filament using biodegradable resin composition having improved whiteness and mechanical properties - Google Patents

Abstract

Disclosed is a filament for a three dimensional printer using a biodegradable resin such as polylactic acid or the like. The filament for a three dimensional printer using a biodegradable resin can solve a whiteness problem by omitting a separate process for adding white pigment or dye in order to process a white filament depending on the use of the biodegradable resin, and secure excellent mechanical properties such as high impact strength or the like. In addition, the present invention relates to a filament for a three dimensional printer by extruding and cooling a biodegradable resin composition, wherein the biodegradable resin composition comprises: (A) 50 to 99.5 wt% of a biodegradable resin having crystals; and (B) 0.5 to 50 wt% of an amorphous resin.

Description

TECHNICAL FIELD [0001] The present invention relates to a three-dimensional printer filament using a biodegradable resin composition having improved whiteness and mechanical properties,

TECHNICAL FIELD The present invention relates to a filament for a three-dimensional printer using a biodegradable resin composition, and more particularly to a filament for a three-dimensional printer using a biodegradable resin composition having improved whiteness and mechanical properties.

A three-dimensional (3-dimensional) printer is a device that produces three-dimensional objects by layering layers of fine thickness by sequentially injecting ink of a specific material. 3D printing is spreading in various fields. In addition to the automotive sector, which is composed of many parts, it is used by many manufacturers for making various models such as medical human body models, household products such as toothbrushes and razors.

Currently, the most widely used material for 3D printing is photopolymer, which is a photocurable macromolecule that solidifies upon receiving light. This accounts for 56% of the total market. The next most popular material is solid, thermoplastic, which is free to melt and solidify. It occupies 40% of the market and metal powder is expected to grow gradually in the future. The shape of the double thermoplastics material may be in the form of filaments, particles or powder powders. The three-dimensional printing of the filament type is faster than the other type in speed, so the productivity is high and the spreading speed is fast.

On the other hand, efforts to reduce greenhouse gases due to global warming have been extensively carried out. As one of the efforts, development of biodegradable polymer materials that are decomposed in nature has been attracting attention. Most of the existing polymers use petroleum resources as basic raw materials, but this may be exhausted in the future. Carbon dioxide generated by mass consumption of petroleum resources is recognized as a main cause of global warming. Therefore, attention has been focused on the development and industrial application of biodegradable polymers using plant resources grown by using carbon dioxide as a raw material.

2. Description of the Related Art Biodegradable polymer materials such as polylactic acid (PLA) have been actively used as a three-dimensional printer filament material. However, most of the three-dimensional printer injection molds have a single color, and about 90% of them are supplied in white. At present, white pigments or dyes are added in order to process white filaments. This can result in the addition of one or more machining processes, which can adversely affect machining time and cost.

Korean Prior Patent Publication No. 2011-0059358 discloses a method of reinforcing impact strength by adding a polyphenylene ether resin to a base resin containing a composition of a polylactic acid resin and a polycarbonate resin However, it is not suitable for resins having various poly (lactic acid) compositions and does not indicate the applicability to three-dimensional printer filaments, and does not mention improvement in whiteness.

Korean Patent Laid-Open Publication No. 2012-0129500 discloses a method for improving the miscibility of components in a blend by adding an ester exchange catalyst to have good mechanical properties, thermal processability and flame retardancy, And / or parts, construction materials, and / or articles, and thus does not indicate the applicability to three-dimensional printer filaments nor does it mention whiteness enhancement.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a process for producing a filament for a three-dimensional printer using a biodegradable resin such as polylactic acid by adding an additional white pigment or dye for processing white filaments Which can solve the whiteness problem while securing excellent mechanical properties, such as impact strength, by using a biodegradable resin.

In order to solve the above problems, the present invention provides a three-dimensional printer filament produced by extruding and cooling a biodegradable resin composition, wherein the biodegradable resin composition comprises (A) 50 to 99.5% by weight of a biodegradable resin having crystals; And (B) 0.5 to 50% by weight of an amorphous resin.

The biodegradable resin having the crystal (A) is a biodegradable polyester resin having crystals prepared by polycondensation of an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, or a mixture thereof with a diol compound. Filament < / RTI >

The biodegradable polyester resin may be selected from the group consisting of polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate-co-terephthalate (PBAT), poly (butylene adipate-co-butylene terephthalate) Polybutylene glutarate-co-terephthalate (PBGT) and polyhydroxybutyrate (PHB). The present invention also provides a three-dimensional printer filament.

The PLA may be at least one selected from the group consisting of poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), stereo complex PLA and stereo block PLA And a filament for a three-dimensional printer.

The amorphous resin (B) may be at least one selected from the group consisting of polycarbonate, acrylonitrile butadiene styrene copolymer, polystyrene, styrene acrylonitrile copolymer, acrylonitrile styrene acrylate wherein the filament is at least one selected from the group consisting of acrylonitrile styrene acrylate copolymer, polymethyl methacrylate, polysulfone, and polyethersulfone. do.

A compatibilizing agent comprising a block copolymer or a graft copolymer for forming a micro phase separation structure between the biodegradable resin having the crystal (A) and the amorphous resin (B) is mixed with the biodegradable (B) Wherein the filament is contained in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the total of the resin composition and the amorphous resin (B).

The block copolymer may be a styrene-ethylene / butylene / styrene (SEBS) block copolymer, a styrene-ethylene / propylene-styrene (SEPS) block copolymer, a methacrylic block copolymer, a polycaprolactone polyester copolymer, The present invention provides a three-dimensional printer filament characterized in that it is at least one selected from the group consisting of poly (caprolactone) polyester / poly (tetramethylene glycol) block polyol copolymer and methacrylate polystyrene copolymer.

The graft copolymer is at least one selected from the group consisting of a polypropylene-maleic anhydride graft copolymer, a polyethylene-maleic anhydride graft copolymer and a polyethylene-glycidyl methacrylate graft copolymer And a filament for a three-dimensional printer.

The filament has a whiteness index of not less than 35.0 and a L * (color L) value of not less than 70 in a whiteness evaluation (ASTM E 313) using a colorimeter.

(ASTM D 648, 4.6 kgf / cm 2) of not less than 57.6 ° C and a tensile strength (ASTM D 638) of not less than 5.72 kgf · cm / Is 738 kgf / cm 2 or more, and the elongation at break (ASTM D 638) is 2.1% or more.

According to the present invention, it is possible to provide a filament for a three-dimensional printer having an excellent whiteness and excellent mechanical properties by mixing an amorphous resin in a proper amount with a biodegradable resin having crystals.

Also, by providing a three-dimensional printer injection molding exhibiting excellent whiteness and mechanical properties as compared with the conventional biodegradable resin composition, a large ripple effect can be obtained in the three-dimensional printer industry.

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as "including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The present inventors have focused on the problem of additional processes for adding white pigments or dyes for processing white filaments in a biodegradable resin filament in a three-dimensional printer using a biodegradable resin such as polylactic acid, As a result of intensive researches, it has been found that when the amorphous resin is mixed with the amorphous resin in a proper amount in the crystalline biodegradable resin, whiteness is improved and excellent mechanical properties are exhibited, leading to the present invention.

Accordingly, the present invention provides a three-dimensional printer filament produced by extruding and cooling a biodegradable resin composition, wherein the biodegradable resin composition comprises (A) 50 to 99.5% by weight of a biodegradable resin having crystals; And (B) 0.5 to 50% by weight of an amorphous resin.

In the present invention, the biodegradable resin having crystal (A) in the present invention is not particularly limited as long as it is a resin capable of improving whiteness according to mixing with amorphous resin described later, but is preferably an aliphatic dicarboxylic acid, Or a biodegradable polyester resin having a crystal prepared by polycondensation of a mixture thereof and a diol compound. Examples of such biodegradable polyester resins include polylactic acid (PLA), polybutylene succinate (PBS), polybutylenedi adipate-co-terephthalate (PBAT), poly (butylene adipate-co-butylene succinate-co-butylene terephthalate ), Polybutylene glutarate-co-terephthalate (PBGT), and polyhydroxybutyrate (PHB). These resins may be used singly or in combination of two or more, preferably PLA.

Generally, PLA is a polyester resin produced by an ester reaction using lactic acid obtained by decomposing corn starch as a monomer, and its structure is shown in the following formula (1).

The PLA may be composed of a repeating unit derived from an L-isomeric lactate, a repeating unit derived from a D-isomeric lactate, or a repeating unit derived from an L, D-isomeric lactate, wherein the PLA is an L-isomer and a D- (Stereocomplex PLA or stereo block PLA) of the repeating units derived from lactic acid alone (PLLA or PDLA) or in combination. 1 shows the process of forming a stereocomplex PLA together with an L-type PLA and a D-type PLA structure. In Table 1, a glass of a single-component L-type PLA (PLLA) and a stereo complex PLA formed at a 50:50 weight% The transition temperature (T _g ), melting temperature (T _m ), crystalline structure and melting enthalpy change were compared.

In the present invention, when PLA is used as the biodegradable polyester resin, PLLA, PDLA, stereocomplex PLA and stereoblock PLA may be used alone or in combination.

When PLLA is used, the repeating units derived from L-isomeric lactic acid are preferably 95% by weight or more, more preferably 97% by weight or more, and most preferably 99% by weight or more in terms of balance of heat resistance and moldability. At this time, it is more preferable that 95 to 100% by weight of the repeating unit derived from the L-isomeric lactic acid and 0 to 5% by weight of the repeating unit derived from the D-isomeric lactic acid are considered.

The PLLA is not particularly limited in terms of molecular weight and molecular weight distribution if it can be processed, but it is preferable to use a PLLA having a weight average molecular weight of 80,000 or more from the viewpoint of balance of mechanical strength and heat resistance of a molded article, and a weight average molecular weight of 90,000 to 500,000 Is more preferable.

When PDLA is used, the repeating units derived from D-isomeric lactic acid are preferably 95% by weight or more, more preferably 97% by weight or more, and most preferably 99% by weight or more in terms of balance of heat resistance and moldability. At this time, it is more preferable that 95 to 100% by weight of the repeating unit derived from the D-isomeric lactic acid and 0 to 5% by weight of the repeating unit derived from the L-isomeric lactic acid are taken into account in consideration of the hydrolysis resistance.

There is no particular limitation on the molecular weight or the molecular weight distribution of the PDLA. However, it is preferable to use a PDLA having a weight average molecular weight of 10,000 or more for increasing the crystallization rate, more preferably 20,000 to 100,000.

When PLA is used as the biodegradable polyester resin in the present invention, the PLA preferably has a melt index of 2 to 15 g / 10 min (210 ° C, 2.16 kg), more preferably 3 to 10 g / 10 min, / 10 min. If the PLA has a melt index of less than 2 g / 10 min or more than 15 g / 10 min, impact strength and processability may be deteriorated.

In the present invention, the biodegradable resin having crystals is contained in an amount of 50 to 99.5% by weight, preferably 70 to 99% by weight, and more preferably 80 to 97% by weight. When the content of the biodegradable resin is less than 50% by weight, the flexibility of the final resin composition may be deteriorated and the yellowing phenomenon may be intensified. When the biodegradable resin content is more than 99.5% by weight, it is difficult to expect the improvement of mechanical properties and whiteness due to excessive flexibility. .

In the present invention, the amorphous resin (B) in the final resin composition prepared by mixing with the biodegradable resin having the above-mentioned crystal structure exhibits sufficient whiteness without any additional pigment or dye addition step, .

The amorphous resin is not particularly limited and includes, for example, polycarbonate, acrylonitrile butadiene styrene copolymer, polystyrene, styrene acrylonitrile copolymer, acrylonitrile Acrylonitrile styrene acrylate copolymer, polymethyl methacrylate, polysulfone and polyethersulfone may be used alone or in combination. Preferably, polycarbonate Resins can be used. When a polycarbonate resin is used, the melt index (ASTM D 1238, 300 ° C, 1.2 kg) of 1 to 20 g / 10 min, preferably 5 to 15 g / 10 min is very advantageous in improving mechanical properties as well as improvement in whiteness .

In the present invention, the amorphous resin is contained in an amount of 0.5 to 50 wt.%, Preferably 1 to 30 wt.%, More preferably 3 to 20 wt.%. , The mechanical properties such as impact strength may be lowered and the whiteness improvement effect may be difficult to be expected. If it exceeds 50% by weight, the flexibility of the final resin composition may be deteriorated.

The present invention may further comprise a compatibilizer for good mixing of the biodegradable resin having crystal (A) and the amorphous resin (B). The compatibilizing agent is a substance having the ability to form and stabilize a micro phase separation structure by alleviating the difference in properties between the biodegradable resin having crystals and the amorphous resin and can improve the mechanical properties such as impact strength while maintaining the whiteness of the final resin composition Can be included in the optimal amount for the purpose. For this purpose, the content of the compatibilizer may be 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the biodegradable resin having the crystal (A) and the amorphous resin (B) . If the content of the compatibilizer is less than 0.5 parts by weight, compatibility with the resin may be weakened, and mechanical properties such as impact strength may be deteriorated. If the content exceeds 10 parts by weight, the compatibilizer may not be effective in improving the physical properties.

The compatibilizing agent may be a block copolymer compatibilizer or a graft copolymer compatibilizer, for example, as long as it is capable of achieving good mixing of the biodegradable resin having (A) crystal and the amorphous resin (B) Preferably, a graft copolymer compatibilizer may be used.

Examples of the block copolymer compatibilizer include styrene-ethylene / butylene / styrene (SEBS) block copolymer, styrene-ethylene / propylene-styrene (SEPS) block copolymer, methacrylic block copolymer, polycaprolactone polyester Ethylene / butylene / styrene (SEBS) block copolymer, styrene (ethylene / butylene / styrene) block copolymers, -Ethylene / propylene-styrene (SEPS) block copolymer may be used.

Examples of the graft copolymer compatibilizer include a polypropylene-maleic anhydride graft copolymer, a polyethylene-maleic anhydride graft copolymer, and a polyethylene-glycidyl methacrylate graft copolymer. Maleic anhydride graft copolymer alone or a mixture of a polyethylene-maleic anhydride graft copolymer or a polyethylene-glycidyl methacrylate graft copolymer in a polypropylene-maleic anhydride graft copolymer Can be used in one form.

The biodegradable resin composition for use in the production of a filament for a three-dimensional printer according to the present invention may further contain other additives in addition to the main components described above, within a range not departing from the intended use or effect. For example, the additive may be added for various applications by further adding a nucleating agent, heat stabilizer, light stabilizer, flame retardant, carbon black, antioxidant, impact modifier, etc., 10 parts by weight.

The molded article formed by the three-dimensional printing method using the filament for a three-dimensional printer according to the present invention is excellent in whiteness so that it can be molded without additional pigment or dye addition process, and mechanical properties such as impact strength are improved. (Whiteness index) of 35.0 or more, L * (color L) value of 70 or more, and IZOD impact strength (ASTM D 256) of 5.72 kgf · cm / (ASTM D 638) of not less than 738 kgf / cm 2 and a breaking point elongation (ASTM D 638) of not less than 2.1 % Or more of a filament for a three-dimensional printer.

The biodegradable resin composition used in the production of the filament for a three-dimensional printer according to the present invention can be produced by a known melt extrusion method for producing a general resin composition. That is, a biodegradable resin having crystals, an amorphous resin, a compatibilizer, and other additives may be mixed at the same time and then melt-extruded in an extruder to produce a desired product.

For example, the components are first mixed in an appropriate amount. At this time, mixing may be performed by arbitrarily selecting mixing means which are well known in the art such as a tumbler mixer, a blending machine, a hopper, and the like. Thereafter, the homogeneously mixed composition is melt-extruded at 170 to 200 DEG C by using a twin-screw extruder and molded into a pellet state. Thereafter, the resin composition molded into pellets is extruded by a single-screw extruder at 170 to 200 ° C, cooled, and wound up to be re-formed into filaments having a constant diameter, and can be used for a three-dimensional printer filament. The filament may be extruded by a single screw extruder having a screw diameter of 20 to 40 mm and a screw length of 100 to 110 mm, cooling the filament using a cooling water bath, and winding the filament into a filament having a diameter of 1.5 to 2 mm.

Hereinafter, a specific embodiment of the present invention will be described.

First, the specifications of the components used in Examples and Comparative Examples of the present invention are as follows.

(1) Biodegradable resin having crystal

A PLA product Ingeo 4032D (melt index 7 g / 10 min (210 캜, 2.16 kg) manufactured by NatureWorks LLC, USA) was used.

(2) Amorphous resin

Polycarbonate product PC-1100 (melt index: 10 g / 10 min (300 캜, 1.2 kg)) manufactured by Lotte Chemical Co., Ltd. was used.

(3) compatibilizer

A polypropylene-maleic anhydride graft copolymer (PH-200, maleic anhydride graft ratio: 3.9%) produced by Lotte Chemical Co., Ltd. was used as a graft copolymer.

(4) White master batch

TiO ₂ (70%) product, which was used in the preparation of the resin composition according to the comparative example.

(5) Phenolic antioxidants

To prevent thermal decomposition of the resin composition, Irganox ( ^R) 1010 manufactured by Ciba Inc. was used.

Example  One

99 parts by weight of biodegradable resin having crystal, 1 part by weight of amorphous resin, 3 parts by weight of compatibilizing agent and 0.1 phr of phenolic antioxidant (0.1 part by weight with respect to 100 parts by weight of total components excluding additives) And extruded in a temperature range of 170 to 200 DEG C in a twin-screw extruder having an L / D ratio of 25 and a diameter of 40 mm, and the extrudate was prepared in the form of pellets. The extruded pellets were dried at 80 DEG C for 12 hours.

Example  2

Pellets were prepared in the same manner as in Example 1, except that 97 parts by weight of biodegradable resin having crystals in Example 1 and 3 parts by weight of amorphous resin were mixed.

Example  3

Pellets were prepared in the same manner as in Example 1, except that 95 parts by weight of biodegradable resin having crystals in Example 1 and 5 parts by weight of amorphous resin were mixed.

Example  4

Pellets were prepared in the same manner as in Example 1, except that 90 parts by weight of biodegradable resin having crystals in Example 1 and 10 parts by weight of amorphous resin were mixed.

Example  5

Pellets were prepared in the same manner as in Example 1, except that 80 parts by weight of biodegradable resin having crystals in Example 1 and 20 parts by weight of amorphous resin were mixed.

Example  6

Pellets were prepared in the same manner as in Example 1, except that 70 parts by weight of biodegradable resin having crystals in Example 1 and 30 parts by weight of amorphous resin were mixed.

Comparative Example  One

Pellets were prepared in the same manner as in Example 1, except that 100 parts by weight of the biodegradable resin having crystals without mixing the amorphous resin in Example 1 was used.

Comparative Example  2

Pellets were prepared in the same manner as in Example 3, except that in Example 3, the white mast batch was mixed instead of the amorphous resin.

The composition (unit: parts by weight) of the resin composition prepared according to the above Examples and Comparative Examples is shown in Table 2 below.

Test Example  One

For the evaluation of the whiteness of the filament for a three-dimensional printer according to the present invention, the resin compositions prepared according to the above Examples and Comparative Examples were extruded using a press molding machine (heating at 190 캜 for 5 minutes and cooling for 5 minutes, Thick specimens were prepared and evaluated for whiteness according to the ASTM E 313 standard using a colorimeter. The results are shown in Table 3 below.

Referring to Table 3, in the specimens prepared by mixing the biodegradable resin having crystals according to the present invention and the amorphous resin in the optimum amounts (Examples 1 to 6), amorphous resin was mixed with 100 parts by weight of biodegradable resin The whiteness was remarkably improved as compared with the test piece (Comparative Example 1). As compared with the case of using the conventional white master batch (Comparative Example 2), whiteness equal to or higher than that of the conventional white master batch can be obtained and sufficient whiteness can be obtained without using pigments or dyes can confirm. However, since the yellowness index (YI) may increase as the amorphous resin content increases, it can be seen that excessive optimal amorphous resin content exists.

Test Example  2

In order to evaluate the physical properties of the filament for a three-dimensional printer according to the present invention, the resin compositions prepared according to Examples 1 to 6 and Comparative Example 1 were extruded at an injection machine (Dongshin Hydraulic Co., Ltd., Korea) having a mold clamping force of 150 tons , And then ASTM test specimens were injection-molded by using the extruder. The prepared specimens were evaluated according to the ASTM standard and the results are shown in Table 4 below.

Referring to Table 4, in the case of the specimens (Examples 1 to 6) prepared by mixing the biodegradable resin having crystals according to the present invention and the amorphous resin in an optimum amount, the amorphous resin was prepared without mixing with 100 parts by weight of the biodegradable resin The impact strength was 142%, the thermal deformation temperature was 102%, the tensile strength was 109%, and the breaking point elongation was 126%, which is improved from the viewpoint of all mechanical properties as compared with the specimen (Comparative Example 1).

The preferred embodiments of the present invention have been described in detail above. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (10)

In a three-dimensional printer filament produced by extruding and cooling with a biodegradable resin composition,
Wherein the biodegradable resin composition comprises (A) 50 to 99.5% by weight of a biodegradable resin having crystals; And (B) 0.5 to 50% by weight of an amorphous resin. The method according to claim 1,
Wherein the biodegradable resin having the crystal (A) is a biodegradable polyester resin having a crystal prepared by condensation polymerization of an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, or a mixture thereof with a diol compound. filament. 3. The method of claim 2,
The biodegradable polyester resin may be at least one selected from the group consisting of polylactic acid (PLA), polybutylene succinate (PBA), polybutylenedi adipate-co-terephthalate (PBAT), polybutylene adipate-co-butylene terephthalate polybutylene glutarate-co-terephthalate (PHB), polyhydroxybutyrate (PHB), and the like. The method of claim 3,
The PLA is at least one selected from the group consisting of poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), stereo complex PLA and stereo block PLA A filament for a three-dimensional printer characterized by. The method according to claim 1,
The amorphous resin (B) may be at least one selected from the group consisting of polycarbonate, acrylonitrile butadiene styrene copolymer, polystyrene, styrene acrylonitrile copolymer, acrylonitrile styrene acrylate acrylonitrile styrene acrylate copolymer, polymethyl methacrylate, polysulfone, and polyethersulfone. 2. A three-dimensional printer filament according to claim 1, wherein the at least one filament is at least one selected from the group consisting of acrylonitrile styrene acrylate copolymer, polymethyl methacrylate, polysulfone and polyethersulfone. The method according to claim 1,
A compatibilizing agent comprising a block copolymer or a graft copolymer for forming a micro phase separation structure between the biodegradable resin having a crystal (A) and the amorphous resin (B) is mixed with a biodegradable , And 0.5 to 10 parts by weight based on 100 parts by weight of the total of the resin (B) and the amorphous resin (B). The method according to claim 6,
The block copolymers may be selected from the group consisting of styrene-ethylene / butylene / styrene (SEBS) block copolymers, styrene-ethylene / propylene-styrene (SEPS) block copolymers, methacrylic block copolymers, polycaprolactone polyester copolymers, Wherein the at least one polymer is at least one selected from the group consisting of caprolactone polyester / poly (tetramethylene glycol) block polyol copolymer and methacrylate polystyrene copolymer. The method according to claim 6,
The graft copolymer is at least one selected from the group consisting of a polypropylene-maleic anhydride graft copolymer, a polyethylene-maleic anhydride graft copolymer and a polyethylene-glycidyl methacrylate graft copolymer A filament for a three-dimensional printer. The method according to claim 1,
Wherein the filament has a whiteness index (WI) of not less than 35.0 and a L * (color L) value of not less than 70 in a whiteness evaluation (ASTM E 313) using a colorimeter. The method according to claim 1,
Wherein the filament has an IZOD impact strength (ASTM D 256) of 5.72 kgf · cm / cm or more, a heat distortion temperature (ASTM D 648, 4.6 kgf / cm 2) And a breaking point elongation (ASTM D 638) of 2.1% or more.