JP2007314906A - Carpet backing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carpet backing having excellent sound absorbing property in addition to recyclability and environmental load reducing property. <P>SOLUTION: The carpet backing is a needle-punched nonwoven fabric made of staple fibers composed mainly of polylactic acid. The average fineness of the staple fiber is 0.8-8 dtex, the average fiber length is 30-100 mm, and at least one surface of the nonwoven fabric has a film form having fine pores by the mutual fusion of the short fibers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carpet backing made of a natural circulation type environment-friendly material and excellent in sound absorption.

  In recent years, there has been concern about global warming caused by mass consumption of petroleum resources and depletion of petroleum resources associated with mass consumption, and environmental awareness is increasing on a global scale. In such a background, there is an urgent need for a natural circulation type environmentally friendly material that is made of plant-derived materials (biomass) and that eventually decomposes into water and carbon dioxide in the natural environment after use.

  However, such biodegradable polymers using biomass have problems of high production costs and low mechanical properties and heat resistance, and have not been used as general-purpose plastics. As a biodegradable polymer utilizing biomass that can solve these problems, polylactic acid, which is a kind of aliphatic polyester, is currently attracting the most attention. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from plants. Among biodegradable polymers using biomass, it has the best balance of mechanical properties, heat resistance and cost. . Development of resin products, fibers, films, sheets and the like using this has been performed at a rapid pitch.

  Under such circumstances, the development of polylactic acid fibers is preceded by agricultural materials and civil engineering materials that make use of biodegradability, but subsequent large-scale applications include clothing, hygiene materials, bedding, Is also expected to be applied to automotive applications.

  In particular, since the enforcement of the Automobile Recycling Law was decided in January 2005, there is a strong demand for easy recyclability of automobiles and their components and reduction of environmental burden.

  As is well known, in automobile interior materials, a large amount of sound absorbing material is used in order to reduce noise from outside the vehicle to passengers. As these automobile sound-absorbing materials, many have been proposed such as glass fibers, urethane foam, miscellaneous felt, and those using high-melting thermoplastic fibers and low-melting thermoplastic fibers (for example, Patent Document 1 and Patent Document 2). reference).

  However, although the sound absorbing material using these materials sufficiently satisfies the sound absorbing property, it is insufficient when considering the compatibility of the automobile material from the viewpoint of easy recyclability and low environmental load. Thus, the present condition is that the sound-absorbing material which consists of a raw material which has easy recyclability and has a low load with respect to an environment has not been proposed yet.

Moreover, although the nonwoven fabric sound-absorbing material in which the surface became film-like by heat treatment has been proposed (see, for example, Patent Document 3), the sound-absorbing material surface is completely formed into a film, and a non-porous film-like material is described. When such a sound absorbing material is used as a carpet backing, there is a concern that the friction resistance with the flooring material is weak and the carpet cannot be fixed.
JP-A-7-3599 JP 2004-145180 A JP 2000-199161 A

  In view of the background of such prior art, the present invention is intended to provide a carpet backing excellent in sound absorption characteristics in addition to easy recyclability and reduction of environmental load.

  In order to solve the above problems, the present invention employs the following means. That is, the carpet backing of the present invention is a needle punched nonwoven fabric composed of short fibers mainly composed of polylactic acid, the average fineness of the short fibers is 0.8 to 8 dtex, and the average fiber length is 30 to 100 mm. A certain thing is used, At least one side of this nonwoven fabric forms the film which has a micropore by melt | fusion of the said short fibers, It is characterized by the above-mentioned.

  According to the present invention, a carpet backing having easy recyclability, low environmental load, and good sound absorption characteristics can be obtained, and such carpet backing can be suitably used particularly as a floor mat backing for automobiles. .

  The present invention, in addition to the above-mentioned problems, that is, easy recyclability and environmental load reduction, has been intensively studied on carpet backing excellent in sound absorption characteristics, and in a nonwoven fabric composed of staple fibers mainly composed of polylactic acid, at least When one side was melted and fused to form a film with specific air permeability, it was found that this problem could be solved at once.

  First, the fibers used in the carpet backing of the present invention must be manufactured from polylactic acid. This is because such polylactic acid fibers are superior to other non-petroleum polymers in terms of cost, spinnability, card passing property, and the like. Here, “polylactic acid fiber” refers to a polymer obtained by polymerizing lactic acid oligomers such as lactic acid and lactide, and the optical purity of L-form or D-form is 90% by weight or more which increases the melting point and improves heat resistance. Preferably, 97 weight% or more is more preferable. A blend of polylactic acid having an optical purity of 90% by weight or more in the L form and polylactic acid having an optical purity of 90% by weight or more in the D form in a ratio of 70/30 to 30/70 is preferable because the melting point is further improved. It is. In addition, components other than lactic acid may be copolymerized as long as the properties of polylactic acid are not impaired, and polymers and particles other than polylactic acid, flame retardants, antistatic agents, matting agents, deodorants, You may contain additives, such as an antibacterial agent, an antioxidant, or a coloring pigment. Moreover, you may contain terminal blockers, such as a carbodiimide compound, for the purpose of the hydrolysis suppression of polylactic acid by hot water treatments, such as dyeing | staining, and the physical property fall suppression with time of a product.

  The molecular weight of such a polylactic acid polymer is preferably 50,000 to 500,000, more preferably 100,000 to 350,000 in terms of weight average molecular weight, which has a good balance between mechanical properties and moldability.

  Moreover, the fiber which consists of another polymer may be mixed with the mixture rate of the range which does not exceed 50 weight% from the point of improving abrasion property and form stability when it is set as a nonwoven fabric. Examples of such other polymer fibers include known fibers such as polyethylene terephthalate fibers, polybutylene terephthalate fibers, polytrimethylene terephthalate fibers, polyamide fibers, acrylic fibers, polyolefin fibers, aromatic polyamide fibers, and flame-resistant fibers. can do. However, among these materials, fibers produced using non-petroleum-based raw materials may be used in excess of 50% by weight as long as the environmental load reduction is not contrary to the concept of the present invention. For example, polytrimethylene terephthalate fiber can be used as the fiber made of such a non-petroleum material.

  The fibers constituting the nonwoven fabric of the present invention are required to be formed of fibers having an average fineness in the range of 0.8 to 8 dtex. When the average fineness is larger than 8 dtex, sufficient sound absorption as a carpet backing cannot be obtained, and when it is smaller than 0.8 dtex, it becomes difficult to produce by a normal melt spinning method, resulting in an increase in cost. There arises a problem that the handleability is lowered. The cross-sectional shape of the fibers forming such a nonwoven fabric is not particularly limited, and known ones such as circles, triangles, and flats can be used. In addition, the average fiber length is preferably in the range of 30 to 100 mm, and more preferably 35 to 60 mm, because the passability when passing the short fibers through the card is good. Furthermore, the fibers constituting the nonwoven fabric are preferably short fibers with crimps because the thickness and basis weight can be easily adjusted.

Moreover, as for the nonwoven fabric of this invention, the fabric weight is 100-1000 g / m < ² >, and the thing within the range whose thickness is 1-50 mm is used preferably. That is, when the basis weight is smaller than 100 g / m ² and the thickness is smaller than 1 mm, the density and thickness for obtaining the sound absorbing effect are impaired, and sufficient sound absorbing properties cannot be obtained. On the other hand, when the basis weight is larger than 1000 g / m ² and the thickness is larger than 50 mm, the weight and the thickness are too large to be used as a carpet backing.

  Furthermore, the nonwoven fabric of the present invention can be mixed with a core-sheath composite fiber in which a thermoplastic polymer having a melting point lower than that of the polylactic acid fiber, which is the main constituent fiber of the nonwoven fabric, is arranged in the sheath portion as a thermal adhesive component. It is preferably used for enhancing the strength and form stability of the nonwoven fabric. This heat-adhesive core-sheath conjugate fiber is preferably composed of a low-melting-point component as a sheath component in the range of 30 to 70% by weight because the effect of heat bonding is good. Furthermore, the melting point of the low melting point component is preferably 40 ° C. or more lower than that of polylactic acid fiber from the viewpoint of form stability after melting and fusion processing.

Furthermore, the nonwoven fabric of the present invention can be manufactured by performing carding after opening, laminating the obtained web with a cross wrapper, and subjecting the obtained fiber assembly to needle punching. The needle driving density in such needle punching is preferably 80 to 400 / cm ² . If the needle driving density is less than 80 / cm ² , the strength required for the carpet backing cannot be obtained. Conversely, if it exceeds 400 / cm ² , the softness of the carpet backing is impaired. become.

  By the way, the carpet backing of the present invention can be obtained by melting and fusing the surface of at least one side of the needle punched nonwoven fabric thus obtained into a specific surface state. That is, the short fibers constituting the surface are melted and fused to form a film. By subjecting such a specific surface state to a fusion / fusion process, this layer resonates with sound waves to become a layer that absorbs specific sound waves and can obtain sound absorption suitable as a carpet backing. .

  That is, heating by a hot roll is preferably employed as a heat treatment method for melting and fusing the surface into a specific surface state. By heating with a hot roll, only one side of the nonwoven fabric can be uniformly melted and fused. The surface temperature of the hot roll is in the range of 170 to 210 ° C., which is higher than the melting point of polylactic acid. If the temperature is lower than 170 ° C., the surface of the needle punched nonwoven fabric is not sufficiently fused. It becomes impossible to get sex. The distance between rolls is preferably set to be smaller than the thickness of the non-processed nonwoven fabric and 1 to 5 mm smaller than the thickness of the unprocessed nonwoven fabric. When the distance between the rolls is made 5 mm or less smaller than the thickness of the non-woven fabric before processing, not only the texture of the product becomes stiff, but also fine pores on the surface are not formed, and sufficient sound absorption cannot be obtained. Furthermore, the processing speed of the hot roll is preferably 1 to 10 m / min, more preferably 1 to 5 m / min or less. When the processing speed is 10 m / min or more, the molten state of the surface is not sufficient, and it is difficult to process into a film. On the other hand, if it is 1 m / min or less, not only the texture of the product becomes stiff, but also the pores on the surface are not formed, and the necessary sound absorbing properties cannot be obtained. The surface temperature of the hot roll is preferably as uniform as possible, and the temperature difference is preferably within ± 3 ° C. at the center and at the end. More preferably, it is within ± 1 ° C.

  According to the heating by the hot roll under the above-mentioned conditions, the surface is melted and fused in a film shape, and then becomes a surface in which fine pores are scattered innumerably, thereby obtaining a carpet backing having good sound absorption. be able to. That is, it can be formed into a shape composed of a molten film that has been melted into a film but has fine pores that have air permeability.

  The diameter of the pores is preferably 1 to 250 μm. More preferably, it is 5-100 micrometers. When the pore diameter is larger than 250 μm, the air permeability as a carpet backing increases, and good sound absorption cannot be obtained.

A carpet backing having an air permeability measured in accordance with JIS L 1096 of 1 to 150 cm ³ / cm ² · sec can provide a nonwoven fabric having an optimum sound absorption peak in the target sound absorption region. This is preferable.

  Furthermore, if the thickness of the part melt | dissolved in the film form is 50-250 micrometers, a sound absorption peak will express in 1000 Hz vicinity required as a carpet backing because a film-like part resonates with a specific frequency.

  Subsequently, in the process of laminating the carpet backing and the carpet base material, it is preferable for the lamination to be bonded with a biodegradable adhesive from the convenience of disposal processing.

  Such biodegradable adhesives include those composed of starch, polybutylene succinate, polycacrolactone, etc., but it is preferable to use polylactic acid based adhesives from the viewpoint of easy recycling, but usually used Adhesives such as SBR, NBR resin, acrylic resin, and polyester resin can be used.

  The bonding method is not particularly limited, and is a method of thermally bonding after laminating using a heat bonding sheet, a method of mixing heat-bonded short fibers in a fiber structure, and thermally bonding nonwoven fabrics, and spraying an adhesive. A method of spraying and bonding non-woven fabrics can be used. Among them, a method of spraying an adhesive and bonding non-woven fabrics is preferable in terms of ease of handling.

  By the method for producing a sound absorbing material of the present invention, a carpet backing having excellent sound absorbing properties in a wide range from a low frequency region to a high frequency region in addition to easy recyclability and low environmental load can be easily obtained.

  Examples of the sound absorbing material of the present invention will be described below.

  In addition, the following method was used as a measuring method of the characteristic in an Example.

A. Average fineness (dtex)
JIS L 1015 (1999) 8.5.1 Based on method A, a small amount of the sample is drawn in parallel with a hammer, placed on a cutting table, and a gauge plate is crimped while keeping it straight with an appropriate force. Then, it was cut into a length of 30 mm with a blade such as a safety razor, and 300 fibers were counted as a set, and the mass was measured to determine the apparent fineness. From the apparent fineness and the equilibrium moisture content measured separately, the fineness was calculated by the following formula to calculate the positive fineness.
Positive fineness (dtex) = D ′ × (100 + Rc) / (100 + Re)
Where D ′: apparent fineness (dtex)
Rc: Official moisture content (%)
Re: Equilibrium moisture content (%).

B. Average fiber length JIS L 1015 (1999) 8.4.1 Based on method A, 200 mg of material was drawn in parallel with a hammer and a staple diagram was made to a width of about 25 cm with a pair-type sorter. At the time of production, the number of times the fibers were grasped and pulled out to arrange all the fibers on the velvet plate was about 70 times. A scaled celluloid plate was placed on top of this and plotted on graph paper. The staple diagram illustrated by this method is equally divided into 50 fiber length groups, the boundary line of each section and the fiber lengths at both ends are measured, 49 boundary fiber lengths are added to the average of the fiber lengths at both ends, and the result is divided by 50. The average fiber length was calculated.

C. Weight per unit (g / m ² )
Based on JIS L 1096 (1999) 8.4.2, three test pieces of 20 cm × 20 cm were collected, and the mass (g) in each standard state was measured, and the mass per 1 m ² (g / M ² ).
S _m = W / A
S _m : basis weight (g / m ² )
W: Mass of test piece in standard state (g)
A: Area (m ² ) of the test piece.

D. Thickness (mm)
Based on JIS L 1096 (1999) 8.5.1, the thickness was measured by applying a pressure of 23.5 kPa for 10 seconds using a thickness measuring device at five different locations of the sample.

E. Air permeability (cm ³ / cm ² · sec)
Based on JIS L 1096 (1999) 8.27.1 A method, using a fragile type tester, after attaching a test piece to one end of a cylinder, an inclination type barometer shows a pressure of 125 Pa by an adjusting resistor. The amount of air passing through the test piece was determined from the table attached to the tester from the pressure indicated by the vertical barometer at that time and the type of air hole used.

F. Sound absorption Measured according to JIS A 1405: 1998.
Three circular test pieces having a diameter of 90 mm were sampled from a carpet sample obtained by laminating a carpet base material and a carpet backing.
As a test apparatus, an automatic perpendicular incidence sound absorption rate measuring device (model 10041A) manufactured by Electronic Sokki Co., Ltd. was used. The impedance tube in this test apparatus had an outer diameter of 101.6 mm, an inner diameter of 91.6 mm, and a total length of 2160 mm.
The test piece was placed so that there was no air layer between one end of the impedance tube and the metal reflector with the carpet backing as the sound wave incident surface. Then, a sound wave in a frequency range of 100 to 2000 Hz is incident on the test piece in a stepwise manner, and the ratio of the acoustic power that enters the test specimen surface (does not return) with respect to the incident acoustic power with respect to the plane wave of that frequency (normal incidence) The sound absorption rate) was measured, and the average value for the three test pieces was calculated.

G. Average pore diameter When a film-like surface is observed with a scanning electron microscope (SEM), it is magnified 100 times, and when the number of islands in the surface exceeds 30 from the field of view of 800 μm length and 1000 μm width, n number 30 were extracted at random, the crossing of each island was measured with image analysis software, and the diameter was calculated from the area in terms of a perfect circle.

[Example 1]
(Carpet backing)
A polylactic acid short fiber having a fineness of 1.7 dtex and a fiber length of 38 mm was passed through a fiber spreader twice to open the fiber, and then the fiber was weighed and a web was created with a parallel card machine. The created web was passed once on each side with a needle punch machine (number of needles 40 / cm ² ), and the fibers were entangled to produce a needle punched nonwoven fabric having a basis weight of 374 g / m ² and a thickness of 2.8 mm.

The obtained nonwoven fabric was set to a temperature difference of 170 ° C. ± 1 ° C. at the center and end of the roll, and the clearance was set to 1.0 mm smaller than the thickness of the nonwoven fabric by a hot roll at a processing speed of 2 m / min. Then, one side was melted and fused to obtain a carpet backing having an air permeability of 4 cm ³ / cm ² · sec and a thickness of 1.1 mm. The average pore diameter of the micropores on the film surface formed by fusion of the fibers was 35 μm.

(Carpet base material)
High yarn Is either of poly lactic acid (BCF) (fineness 2000 dtex, 96 filament) and 2 Hongo yarn, 160 times / m after twisting was carried out, 1 to polyethylene terephthalate spunbond primary backing having a basis weight of 100 g / ^{m 2} / 10 gauge, stitch 7.5, and pile length 10 mm were tufted using a tuft machine to obtain a carpet substrate.

(carpet)
The carpet backing obtained above was spray-coated with 20 g / cm ² of acrylic resin and bonded to the carpet substrate obtained above to obtain a carpet.
The sound absorption was measured and found to be as good as 88% at 1000 Hz and 96% at 1250 Hz.

[Example 2]
(Carpet backing)
A carpet backing with an air permeability of 7 cm ³ / cm ² · sec and a thickness of 2.7 mm was obtained in the same manner as in Example 1 except that the clearance during hot roll processing was 1.8 mm. The average pore diameter of the micropores on the film surface formed by fusing the fibers was 44 μm.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.
The sound absorptivity was as good as 76% at 1000 Hz and 100% at 1250 Hz.

[Example 3]
(Carpet backing)
A carpet backing with an air permeability of 17 cm ³ / cm ² · sec and a thickness of 1.6 mm was obtained in the same manner as in Example 1 except that polylactic acid short fibers having a fineness of 3.3 dtex and a fiber length of 51 mm were used. The average pore diameter of the micropores on the film surface formed by fusion of the fibers was 75 μm.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.
The sound absorptivity was as good as 95% at 1000 Hz and 90% at 1250 Hz.

[Example 4]
(Carpet backing)
A carpet backing with an air permeability of 130 cm ³ / cm ² · sec and a thickness of 2.4 mm was obtained in the same manner as in Example 1 except that polylactic acid short fibers having a fineness of 6.6 dtex and a fiber length of 51 mm were used. The average pore diameter of the micropores on the film surface formed by fusing the fibers was 212 μm.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.
The sound absorption was as good as 80% at 1000 Hz and 100% at 1250 Hz.

[Comparative Example 1]
(Carpet backing)
A polylactic acid short fiber having a fineness of 1.7 dtex and a fiber length of 51 mm was passed through a fiber spreader twice to open the fiber. The fiber was weighed and a web was created with a parallel card machine. The created web is passed once on each side with a needle punch machine (number of needles 40 / cm ² ), the fibers are entangled, and a needle punched nonwoven fabric with a basis weight of 374 g / m ² and a thickness of 2.8 mm is created. A backing was used.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.

[Comparative Example 2]
(Carpet backing)
A polylactic acid short fiber having a fineness of 3.3 dtex and a fiber length of 51 mm was passed through a fiber spreader twice to open the fiber, and then the fiber was weighed and a web was created with a parallel card machine. The prepared web is passed once on each side with a needle punch machine (number of needles 40 / cm ² ), the fibers are entangled to create a needle punched nonwoven fabric with a basis weight of 377 g / m ² and a thickness of 2.5 mm, A backing was used.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.

[Comparative Example 3]
(Carpet backing)
A polylactic acid short fiber having a fineness of 6.6 dtex and a fiber length of 51 mm was passed through a fiber spreader twice to open the fiber, and then the fiber was weighed and a web was created with a parallel card machine. The prepared web is passed once on each side with a needle punch machine (number of needles 40 / cm ² ), the fibers are entangled, and a needle punched nonwoven fabric with a basis weight of 374 g / m ² and a thickness of 3.4 mm is made, and carpet A backing was used.

(Carpet base material)
A carpet base material was obtained in the same manner as in Example 1.

(carpet)
A carpet was obtained in the same manner as in Example 1 except that the carpet backing obtained above was used.

  As is clear from Table 1, the carpet backings of Examples 1 to 4 exhibited excellent sound absorption, but the carpet backing of the comparative example was inferior in sound absorption compared to the examples. there were.

  The sound-absorbing material of the present invention exhibits excellent sound-absorbing properties and achieves both easy recyclability and low environmental impact, and therefore can be suitably used for automotive applications, architectural applications, civil engineering applications, household appliance applications, and audio equipment applications. .

  Moreover, according to the method for producing a sound absorbing material of the present invention, it is possible to easily obtain a sound absorbing material having excellent sound absorbing properties in addition to easy recyclability and low environmental load.

This figure is a photograph showing the surface shape of an example of the nonwoven fabric constituting the carpet backing of the present invention.

Claims (4)

  A needle punched nonwoven fabric composed of staple fibers mainly composed of polylactic acid, wherein the nonwoven fabrics have an average fineness of 0.8 to 8 dtex and an average fiber length of 30 to 100 mm. A carpet backing comprising a film having at least one surface of which has fine pores formed by fusion of the short fibers.   The carpet backing according to claim 1, wherein the micropores have an average pore diameter of 1 to 250 µm. The carpet backing of Claim 1 or 2 whose air permeability measured based on JISL1096 is 1-150cm < ³ > / cm < ² > * sec.   The carpet backing according to any one of claims 1 to 3, wherein the carpet backing is an automobile interior material used as an automobile floor mat backing.