JP5129068B2 - Composite fiber - Google Patents

Description

  The present invention relates to a composite fiber composed of polyolefin and polylactic acid containing a biomass-derived monomer component as a raw material.

  Polyolefins such as polyethylene (PE) are widely used all over the world in various application fields such as various fibers, sheets, films, containers and the like because they are excellent in mechanical strength and chemical stability and inexpensive.

  However, these resins are made from limited fossil resources, and incineration is the mainstream for disposal because they are hardly decomposed in the natural environment. It is a big social problem as one of the causes.

  In contrast, plants that are the origin of biomass can produce plant biomass such as starch, cellulose, and lignin by photosynthesis from solar energy, carbon dioxide, and water. Therefore, if these biomass-derived components are used as resin raw materials, the amount of fossil resources used can be suppressed, and even if they are incinerated after use and decomposed into carbon dioxide and water, they are again planted by photosynthesis. In other words, the carbon source constituting this is to build a life cycle of the circulatory system, and can be made the ultimate recycling material. Therefore, new generation of carbon dioxide, which becomes a greenhouse gas, can be reduced by using biomass-derived components as raw materials. This has recently been referred to as “carbon neutral” and is considered desirable in the future. (For example, see Non-Patent Document 1)

  For example, the Japan Chemical Technology Strategy Promotion Organization has proposed a “biomass complex concept” in which sugarcane juice is fermented instead of petroleum to produce alcohol, which is then converted into ethylene and propylene by chemical reaction. It has been reported that development has begun. (For example, see Non-Patent Document 2.) In addition, Dow Chemical Company in the United States and Crystal Cebu, a major alcoholic and refined sugar company in Brazil, are aiming to start operations in 2011 from ethanol to ethylene, LLDPE ( Announced that it would build an integrated factory up to linear low density polyethylene. (For example, refer nonpatent literature 3.)

Thus, the polyolefin containing biomass-derived carbon is in the stage of being studied from small scale production to industrial production.
Biomass / Nippon Comprehensive Strategies, Ministry of Agriculture / Water, Ministry of Environment / Ministry of Economy, Trade and Industry press release, July 30, 2002 Mainichi Newspaper December 12, 2006 Petrochemical Shinpo, No. 4168, pages 6-7 (issued July 27, 2007) Polylactic acid is also a biomass-derived polymer, which is ultimately decomposed into carbon dioxide and water in the natural environment. It can be said that the carbon dioxide emitted is suitable for carbon neutrality.

  An object of the present invention is to provide a composite fiber composed of polyolefin and polylactic acid, which can suppress the consumption of petroleum resources and suppress the net increase of carbon dioxide into the atmosphere upon disposal.

The present inventors have intensively studied to solve the above problems, and have come to the idea that this object can be achieved if a predetermined amount or more of the raw material monomer of polyolefin is derived from biomass. That is, the composite fiber of the present invention has the following configuration.
(A) A composite fiber comprising a biomass-derived polyolefin and polylactic acid, wherein the composite fiber is a short fiber having a fiber length of 5 to 150 mm, which is obtained by measuring radioactive carbon (carbon 14) in the polyolefin. A composite fiber having a biomass-derived carbon content of 70% or more, wherein the polyolefin constitutes at least part of the outer peripheral surface of the fiber cross section, and the other part is made of polylactic acid.
(B) The composite fiber according to (a), wherein the polyolefin is polyethylene or a copolymer thereof.
(C) According to the method described in ASTM D1238, the polyethylene is a high-density polyethylene whose MFR measured at a temperature of 190 ° C. and a load of 20.2 N (2160 gf) is 10 to 60 g / 10 min. The composite fiber according to (b).

  The composite fiber of the present invention uses a polyolefin having a biomass-derived carbon content of 70% or more as measured by radioactive carbon (carbon 14) measurement as a constituent component. It greatly contributes to the suppression of depletion, and can increase the amount of carbon dioxide, which is a causative agent of global warming, in the atmosphere during incineration.

  The composite fiber of the present invention stably retains the same physical properties as those obtained by using polyolefins made of petroleum-based raw materials, despite using polyolefins made from biomass-derived components. It becomes.

  In addition, since the composite fiber of the present invention uses biomass-derived polylactic acid as another component for polyolefin, it can have a lower environmental impact.

  Moreover, the nonwoven fabric using the conjugate fiber of the present invention has softness excellent in fluff resistance, texture and feel, and can be suitably used for absorbent articles, sanitary materials, wipers and the like.

Hereinafter, the present invention will be described in detail.
The conjugate fiber of the present invention needs to contain a polyolefin that uses a biomass-derived monomer component as a raw material.

  Examples of the polyolefin in the present invention include polyethylene, polypropylene and the like, and polyethylene or a copolymer comprising polyethylene is preferable. Specifically, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene are preferable, and basically have physical properties equivalent to those derived from conventional fossil resources.

  Further, the melt viscosity of the polyolefin in the present invention is preferably 10 to 60 g / 10 min in MFR measured at a temperature of 190 ° C. and a load of 20.2 N (2160 gf) according to the method described in ASTM D 1238. More preferably, it is 20-40 g / 10min. An MFR of less than 10 g / 10 minutes is not preferable because melt extrusion tends to be difficult. On the other hand, an MFR exceeding 60 g / 10 min is not preferable because it tends to be difficult to fiberize well by melt extrusion or the mechanical strength of the fiber is lowered.

  In the present invention, the biomass-derived polyolefin needs to have a biomass-derived carbon content of 70% or more of the total carbon constituting the polyolefin, preferably 80% or more, and more preferably 90%. %, Particularly preferably 100% is occupied by biomass-derived carbon. When the abundance ratio of the biomass-derived carbon is less than 70%, it is not in line with the gist of the present invention to achieve carbon neutrality for polyolefins by replacing materials made of conventional petroleum resources with biomass-derived materials. It becomes.

  The biomass-derived carbon in the present invention refers to carbon existing in a polyolefin synthesized by using carbon that was present as carbon dioxide in the atmosphere as carbon dioxide assimilated in the plant and synthesized as a raw material. Yes, it can be identified by measuring radioactive carbon (carbon 14).

  Here, the meaning of measuring radioactive carbon (carbon 14) in specifying the abundance ratio of biomass-derived components in the present invention will be described below. In the upper part of the atmosphere, the reaction in which cosmic rays (neutrons) collide with nitrogen atoms to generate 14 carbon atoms continues, and since this circulates throughout the atmosphere, It is measured that carbon 14 is contained in a certain ratio [107 pMC (percent modern carbon) as an average]. On the other hand, because the carbon 14 atoms confined in the ground are isolated from the above circulation, only the reaction to return to nitrogen atoms occurs with a half-life of 5,370 years while emitting radiation. Almost no 14 carbon atoms remain in the fossil raw materials. Therefore, by measuring the concentration of carbon 14 in the target sample and calculating backward using the carbon 14 content ratio [107 pMC] in the atmosphere as an index, the ratio of biomass-derived carbon in the carbon contained in the sample is calculated. Can be sought.

  In addition, in the measurement of radioactive carbon (carbon 14), the content ratio of biomass-derived components can be analyzed even with respect to recycled polyolefin. But it is an effective technique. Therefore, the polyolefin of the present invention includes not only a polyolefin newly obtained by polymerizing a biomass-derived component but also a recycled polyolefin containing a biomass-derived polyolefin.

  As described above, as the polyolefin in the present invention, the abundance ratio of biomass-derived carbon depending on the measurement of radioactive carbon (carbon 14) accounts for 70% or more of the total carbon constituting the olefin skeleton, Thereby, it is possible to suppress a net increase of carbon dioxide in the atmosphere during incineration disposal. Here, the net increase in carbon dioxide means an increase in carbon dioxide caused by fossil resources that does not fall under carbon neutrality.

  As a method for producing a polyolefin derived from biomass in the present invention, for example, in the case of polyethylene, starch and sugar obtained from corn, sugarcane, sweet potato, etc. are fermented by microorganisms to produce bioethanol, which is dehydrated to produce ethylene. 100% polyethylene derived from biomass can be obtained by producing and further polymerizing.

  In addition, as a method for producing a polyolefin having a biomass-derived carbon content of 70% or more and less than 100%, it may be produced by polymerizing an olefin consisting only of a biomass-derived olefin and a petroleum-based material, You may manufacture by blending the polyolefin chip | tip which consists only of a biomass-derived polyolefin chip | tip and a petroleum-type raw material.

  As the conjugate fiber of the present invention, it is necessary that polylactic acid is used together with polyolefin derived from biomass.

  Examples of polylactic acid used in the present invention include poly-D-lactic acid, poly-L-lactic acid, poly-DL-lactic acid that is a copolymer of poly-D-lactic acid and poly-L-lactic acid, poly-D-lactic acid, and poly-L-lactic acid. (Stereo complex), poly D-lactic acid and hydroxycarboxylic acid copolymer, poly L-lactic acid and hydroxycarboxylic acid copolymer, poly D-lactic acid or poly L-lactic acid and aliphatic dicarboxylic acid, and Copolymers with aliphatic diols or blends thereof can be mentioned.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above, and among them, the melting point is preferably 120 ° C. or higher.

  The melting point of L-lactic acid and D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the proportion of any component is about 10 mol%. Then, the melting point is about 130 ° C.

  Furthermore, when the proportion of any of the components is 18 mol% or more, the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g, which is almost completely amorphous. When such an amorphous polymer is used, it becomes difficult to heat-stretch particularly in the production process, and it becomes difficult to obtain high-strength fibers. Even if fibers are obtained, heat resistance and wear resistance It is not preferable because it is inferior to

  Therefore, as polylactic acid, L / D or D / which is the content ratio (molar ratio) of L-lactic acid and D-lactic acid indicated by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. L is preferably 82/18 or more, more preferably 90/10 or more, and even more preferably 95/5 or more.

  Among polylactic acids, a mixture (stereocomplex) of poly D-lactic acid and poly L-lactic acid as described above is particularly preferable because it has a high melting point of 200 to 230 ° C. and high strength in a high temperature atmosphere. .

In the conjugate fiber of the present invention, it is necessary that the polyolefin constitutes at least a part of the outer peripheral surface of the fiber cross section, and the other part is made of polylactic acid. As a result, in the conjugate fiber of the present invention, a polyolefin such as polyethylene, which is a soft polymer, constitutes at least a part of the outer peripheral surface of the fiber cross section. It comes to have. In addition, in short fiber nonwoven fabrics and spunbond nonwoven fabrics composed of these composite fibers, heat treatment is performed on polyolefins such as polyethylene, and the texture (softness), feel to the touch, fuzz resistance, etc. are good. Become. And in the nonwoven fabric of the low fabric weight of about 20 g / m < ² > or less, it becomes what can be used conveniently for absorbent articles, such as a paper diaper.

  The composite fiber of the present invention is a composite fiber comprising biomass-derived polyolefin and polylactic acid as constituent components, and the structure thereof is, for example, a concentric or eccentric core-sheath type, a parallel type, or a sea-island type. May be. Among them, the concentric core-sheath type composite fiber is preferable because it has good heat-fusibility and constant physical properties. In addition, it may have an irregular cross-sectional structure or a split structure.

  The ratio of polyolefin and polylactic acid in the conjugate fiber of the present invention is not particularly limited, but is preferably in the range of 30/70 to 70/30 in terms of volume ratio from the viewpoint of operability and cost.

  The composite fiber of the present invention includes known antioxidants, ultraviolet absorbers, lubricants, pigments, antifouling agents, stabilizers, flame retardants, antibacterial agents, colorants, etc., as long as the effects of the present invention are not hindered. It may be added.

The composite fiber of the present invention may be cut into a fiber bundle in which several thousand to several millions are assembled and used as a short fiber having a fiber length of about 5 to 150 mm and then used for a spun yarn or a short fiber nonwoven fabric.

  In addition, the composite fiber of the present invention may be used alone, but is also suitable for use with other fibers, and is used by mixing, knitting, fine spinning, knitting, knitting, knitting. May be a mixed nonwoven fabric. Other fibers to be mixed include synthetic fibers such as polyester, nylon, acrylic and aramid, rayon fibers such as viscose, cupra and polynosic, solvent-spun cellulose fibers such as lyocell, silk, cotton, hemp, wool and other beasts. A hair fiber is mentioned.

  Next, the use of the nonwoven fabric using the conjugate fiber of the present invention and the fineness of the conjugate fiber usable for this will be described. The fineness range can be wide, ranging from those that require very fine ones, such as battery separators, to thick ones that are required for civil engineering special applications that can withstand high earth pressure. is there. For example, a battery separator or the like uses a fineness of 1 dtex or less, and is used as a sanitary material such as a diaper, sanitary product, sweat-absorbing pad, sebum removing sheet material, and a towel. , About 0.2 to 6 dtex, and about 0.5 to 100 dtex when used as agricultural materials such as a beak sheet, a herbicidal sheet, a fruit protection bag, and a heat insulation sheet. In addition, packaging materials, disposable seat covers for airplanes and passenger vehicles, toilet seat covers, heat insulation materials for clothes, shaping materials, air filters, oil adsorbent materials, wipers (disposable household wipes, glasses wipes, floor wipes, tatami wipes) About 0.5-100 dtex can be used as medical materials such as general materials such as etc., daily life materials, surgical gowns, masks and hats.

  In addition, the heat bonding treatment method in the nonwoven fabric is roughly divided into a non-woven fiber assembly using a hot through air method in which hot air or the like is used to bond the majority of the intersections of fibers and an embossing roll or the like. It can be classified into two types, a point thermocompression bonding method in which the parts are thermally bonded. As the former hot-through air method, for example, there is a method in which a nonwoven fabric aggregate is laminated and then introduced into a hot-air circulating rotary dryer to melt and solidify a low melting point component to obtain a composite fiber nonwoven fabric. This thermal through-air method is a good thermal bonding treatment method in order to obtain a bulky nonwoven fabric when using crimped fibers. The latter point thermocompression bonding method is disclosed in, for example, Japanese Patent No. 2103007. As described above, there is a method of embossing a non-woven fiber assembly at a temperature 15 to 30 ° C. lower than the melting point of the fiber. This point thermocompression bonding method has an effect that a nonwoven fabric having a good texture can be obtained.

Although the range of the basis weight in the nonwoven fabric using the conjugate fiber of the present invention is not particularly limited, it is easy to manufacture a nonwoven fabric with a uniform basis weight, the point thermal compression processing, and the formation of the cross-sectional structure of the point thermal compression part. Is 3 to 2000 g / m ² . Among these, in consideration of the texture and softness, 3~100g / ^{m 2} of the above range is preferred. In particular, in sanitary materials, 5 to 30 g / m ² is preferable, but the fineness and basis weight values do not limit the present invention.

  The manufacturing method of the composite fiber of the present invention will be described using a manufacturing example in the case where the above-described fiber bundle in which several thousand to several millions are gathered and short fibers are used. Polyolefin and polylactic acid with an existing ratio of biomass-derived carbon of 70% or more are melt-spun using a normal composite spinning device (concentric core-sheath type composite spinning device), cooled, oiled, and then stretched. Without winding up. The undrawn yarn is focused on a tow of several hundred thousand to two million dtex, drawn at a draw ratio of 2 to 5 times, a draw temperature of 40 to 80 ° C., and subjected to heat treatment at 80 to 120 ° C. Subsequently, after performing mechanical crimping with a push-in crimper, finishing oil is applied and dried with a dryer, and further cut into a target length with a cutter such as an EC cutter to obtain short fibers.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In addition, the measuring methods, such as a characteristic value in an Example, are as follows. The method for measuring MFR of polyolefin is as described above.
(1) Melting point (° C)
Using a differential scanning calorimeter DSC-2 manufactured by Perkin Elma Co., Ltd., measurement was performed under the condition of a temperature increase rate of 20 ° C./min.
(2) Single yarn fineness (dtex)
It measured by the method of JIS L-1015 7-5-1A.

(3) Tensile strength of nonwoven fabric (cN / 25mm width)
The nonwoven fabric was cut into strips having a width of 25 mm and a length of 150 mm to prepare a sample. This sample was stretched and cut using a UTM-4 type Tensilon manufactured by Orientec Corp. under the conditions of a grip interval of 100 mm and a tensile speed of 100 mm / min, and the maximum strength was read. In the present invention, a tensile strength of 1000 cN or more is assumed to have a practical strength.
(4) Bending softness of non-woven fabric (cm)
Based on the 45 degree cantilever method described in JIS L-1096, the moving distance (cm) until the tip of the nonwoven fabric contacted the 45 degree slope was measured. In the present invention, the flexibility is good when the bending resistance (movement distance) is less than 10 cm, and the flexibility is poor when it is 10 cm or more.
(5) Texture of non-woven fabric The softness of the non-woven fabric was sensory-evaluated by a hand test by 10 panelists. When 9 or more out of 10 people evaluated that the texture was soft, ○, when 5 to 8 people evaluated that it was soft, Δ, and when the number was 4 or less, ×. The case of ○ was regarded as acceptable.

(6) Fluffiness Ten panelists visually inspected the nonwoven fabric. When 9 or more out of 10 people evaluated that there was no or almost no fluff, it was evaluated as ◯ when 9 or more out of 10 people evaluated that the fluff was clearly recognized, and x in other cases. The case of ○ was regarded as acceptable.
(7) Biomass-derived carbon abundance ratio by measurement of radioactive carbon (carbon 14) The sample was subjected to an accelerator mass spectrometer (AMS) to measure the carbon 14 content. Carbon dioxide in the atmosphere contains a certain amount of carbon 14 (because neutrons collide with nitrogen in the upper atmosphere to generate carbon 14), but fossil raw materials such as petroleum contain carbon 14. 14 (although carbon 14 emits radiation in the ground and changes to nitrogen with a half-life of 5,370 years). On the other hand, the present proportion of carbon 14 in the atmosphere is measured to be a specific value [107 pMC (percent modern carbon) on average], and existing plants that carry out photosynthesis take in carbon 14 at this proportion. It is known that Therefore, the ratio of biomass-derived carbon in the carbon contained in the sample can be determined by measuring the total carbon and carbon 14 content in the sample. (See formula below)
Content ratio of biomass-derived carbon (%) = (amount of carbon derived from biomass in sample / total amount of carbon in sample) × 100

Example 1
Polylactic acid (melting point: 170 ° C.) as the core, high-density polyethylene (MFR; 20.4, melting point: 130 ° C.) having only biomass-derived carbon as the sheath, 1014 pores, circular cross-section concentric core-sheath composite spinning Using a die, weighed so that core: sheath = 50: 50, and melt-spun at a spinning temperature of 230 ° C. and a spinning speed of 700 m / min to obtain an undrawn yarn of a composite fiber. Next, the obtained undrawn yarn was drawn at a drawing temperature of 65 ° C. and a draw ratio of 3.20 times, then crimped by a push-type crimper and then dried at 65 ° C. after applying the finishing oil. The fiber length was cut to 51 mm to obtain a core-sheath type composite fiber having a fineness of 2.2 dtex.

The obtained core-sheath type composite fiber 100% was put on a card machine, and a web having a weight per unit area of 18 g / cm ² was prepared with a random weber. This web was passed through a continuous heat treatment machine and heat-sealed for 1 minute at 135 ° C. to produce a 22 g / cm ² nonwoven fabric. Table 1 shows the results of evaluating the tensile strength, stiffness and texture of this nonwoven fabric.

(Examples 2-3)
Nonwoven fabrics of Examples 2 to 3 were produced in the same manner as Example 1 except that the polyolefin derived from biomass in the sheath part of the core-sheath composite fiber was used as shown in Table 1. The obtained results are shown in Table 1.

(Example 4)
Example 1 except that the sheath portion of the core-sheath composite fiber is low density polyethylene (MFR; 38.0, melting point: 110 ° C.) having only biomass-derived carbon, and the heat fusion temperature at the time of producing the nonwoven fabric is changed. A nonwoven fabric of Example 4 was produced in the same manner as described above. The results obtained are shown in Table 1.

(Example 5-6)
Example 1 except that polylactic acid is used as a core, high-density polyethylene (MFR; 20.4, melting point; 130 ° C.) having only biomass-derived carbon is used as a sheath, and the core-sheath ratio is shown in Table 1. In the same manner, nonwoven fabrics of Examples 5 to 6 were produced. The results obtained are shown in Table 1.

(Comparative Example 1)
A nonwoven fabric of Comparative Example 1 was produced in the same manner as in Example 1 except that the sheath of the core-sheath composite fiber was changed to petroleum-derived high-density polyethylene (MFR; 20.1, melting point: 130 ° C.). The results obtained are shown in Table 1.

(Comparative Examples 2-3)
Example 1 except that polylactic acid is the core, petroleum-derived high-density polyethylene (MFR; 20.4, melting point: 130 ° C.) is the sheath, and the core-sheath ratio is as shown in Table 1. Thus, nonwoven fabrics of Comparative Examples 2 to 3 were produced. The obtained results are shown in Table 1.

(Comparative Example 4)
A nonwoven fabric of Comparative Example 4 was produced in the same manner as in Example 1 except that the polyolefin derived from biomass in the sheath portion of the core-sheath composite fiber was used as shown in Table 1. The results obtained are shown in Table 1.

(Comparative Example 5)
A nonwoven fabric of Comparative Example 5 was produced in the same manner as in Example 1 except that the sheath of the core-sheath composite fiber was made of high-density polyethylene having only biomass-derived carbon (MFR; 80.4, melting point; 130 ° C.). . The obtained results are shown in Table 1.

  As is apparent from Table 1, Examples 1 to 6 satisfying the requirements of the present invention were sufficiently strong in the nonwoven fabric, very soft in texture, and good without fuzz. And since the component derived from biomass was contained more than predetermined amount, there was little environmental impact and it was in accordance with the main point of carbon neutral.

  On the other hand, in Comparative Examples 1-3, since it is a composite fiber which consists only of the conventional petroleum-type material, it was a thing inferior in a physical property. However, since it does not contain any biomass-derived components, it has no effect on reducing the environmental load.

  Also, Comparative Example 4 was inferior in physical properties. However, since the biomass-derived component is contained in less than a predetermined amount, it does not have a sufficient effect of reducing the environmental load.

Regarding Comparative Example 5, since the MFR of the polyethylene in the sheath portion was not within the range of the appropriate value, the mechanical strength of the fiber was lowered, and the tensile strength of the nonwoven fabric was remarkably low.

Claims (3)

A composite fiber comprising a biomass-derived polyolefin and polylactic acid, wherein the composite fiber is a short fiber having a fiber length of 5 to 150 mm, and the biomass-derived carbon as measured by radioactive carbon (carbon 14) in the polyolefin The composite fiber, wherein the abundance ratio is 70% or more, the polyolefin constitutes at least a part of the outer peripheral surface of the fiber cross section, and the other part is made of polylactic acid. The composite fiber according to claim 1, wherein the polyolefin is polyethylene or a copolymer thereof. According to the method described in ASTM D 1238, the polyethylene is a high density polyethylene having an MFR measured at a temperature of 190 ° C. and a load of 20.2 N (2160 gf) of 10 to 60 g / 10 min. Item 3. A composite fiber according to Item 2.