JPS63175113A - Blend structure of polyethylene with polypropylene - Google Patents

Abstract

PURPOSE:To obtain the titled structure, capable of providing a soft nonwoven fabric having good feeling and useful as disposable diapers, etc., by melt spinning a linear low-density copolymer of ethylene and octene-1 having a specific density, melt index and heat of fusion and crystalline PP having a specific melt index. CONSTITUTION:The aimed blend structure obtained by blending (A) 99-50wt.% linear low-density polyethylene which is a linear low-density copolymer of ethylene and octene-1, containing 1-15wt.% octene-1 and having 0.900-0.940g/cm<3> density, 25-100g/10min melt flow rate measured by the method of ASTM D-1238 (E) and >=25cal/g heat of fusion with (B) 1-50wt.% crystalline polypropylene having <=20g/10min melt flow rate measured by the method of ASTM D-1238 (L) and melt spinning the resultant blend.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a blend structure of linear low density polyethylene and crystalline polypropylene.

In particular, it provides a nonwoven fabric that is more suitable in terms of softness and texture.

BACKGROUND OF THE INVENTION Nonwoven fabrics containing fibers having conventionally different melting temperatures are well known in the art. Fibers with lower melting temperatures act as adhesives to bond fibers with higher melting temperatures. Polyethylene and polypropylene containing fibers are often used as nonwoven fabrics because they have relatively low melting temperatures and other desirable properties. However, since polyethylene is difficult to spin at high speeds, it has been difficult to obtain nonwoven fabrics containing polyethylene and polypropylene using the so-called spunbond method, which involves continuous spinning and web preparation. It was unsatisfactory as an adhesive because of its poor spinning properties.

In addition, low-density polyethylene and high-density polyethylene have been used as polyethylene fibers, but recently,
As shown in JP-A No. 209010 and JP-A-60-1941), linear low-density polyethylene obtained by copolymerizing ethylene and octene-1 has come to be used.

(Problem to be solved by the invention) In recent years, spunbond method has been used to obtain nonwoven fabrics.

Alternatively, in order to simplify the process of obtaining multifilament threads and reduce manufacturing costs,
The trend is becoming stronger. However, although the spinnability required for high-speed spinning can be satisfied in the high-temperature region using the linear low-density polyethylene alone obtained by the methods described in both of the above publications that specify the density and melt index, the spinnability is limited by the temporal stability. However, they were still dissatisfied. In other words, by setting the spinning temperature considerably higher than the melting temperature of linear low-density polyethylene, high-speed suction is possible and it is certainly possible to obtain fine denier fibers, but over time the spinneret surface gets dirty, the thread surface becomes curly, and it is possible to obtain fine denier fibers. The problem of thread breakage occurs.

An object of the present invention is to solve the above-mentioned problems and provide a blend structure that can perform high-speed suction during yarn spinning and has stable operability over time.

(Means and effects for solving the problem) That is, the present invention is a linear low-density copolymer of ethylene and octene-1 containing substantially 1 to 15% by weight of octene-1,
The density is 0.900 to 0.940 g/cm3, the melt index is 25 to 100 g/10 minutes as measured by ASTM D-1238 (E) method, and the heat of fusion is 25 ca.
Linear low density polyethylene consisting of l/g or more is 99-5
0% by weight and melt index ASTM D-123
8(E), consisting of 1 to 50 weight percent of crystalline void propylene smaller than 20 g/10 min, as measured by the method of 8(E);
The gist is a melt-spun blend structure.

In the present invention, the melt index is measured by ASTM method D-1238(E).

In the present invention, the heat of fusion is measured as follows. Perkin-Elmer
Approximately 5 mg of a sample is collected using a DSC-2C type analyzer manufactured by Kogyo Co., Ltd., and the sample is determined from a DSC curve obtained by raising the temperature from room temperature at a scan rate of 20° C./min according to the device manual.

In addition to ethylene and octene-1, the linear low-density polyethylene used in the blend structure of the present invention includes:
It may contain up to 15% by weight of other α-olefins based on the weight of octene-1. Further, additives such as a moisture absorbent, a lubricant, a pigment, a dye, a stabilizer, and a flame retardant may be added to the linear low-density polyethylene.

In the present invention, octene-1 of linear low density polyethylene
If the content exceeds 15% by weight, finer fineness fibers will be obtained.On the other hand, if it is less than 1% by weight, the resulting fibers will be stiff. The fit is not good.

In the present invention, the density of linear low density polyethylene is 0.9
If it exceeds 40g/cm3, it will not be possible to reduce the weight of the fiber, and on the contrary, the weight will be 0.
．． If it is less than 9008/cm', it is difficult to obtain high performance fibers.

The reason why the melt index of linear low-density polyethylene is limited to 25 to 100 g/10 minutes in the present invention is that if linear low-density polyethylene is used alone, the deformation of the discharged yarn will be smooth if the melt index is less than 25 g/10 minutes. As a result, high-speed suction in the spinning process is not possible. Moreover, if it exceeds 100 g/10 minutes, the viscosity is too low, causing fiber diameter unevenness, and the performance of the obtained fibers is poor.

The melt viscosity of both polyethylene and polypropylene is a particularly important requirement for the blend structure in the present invention. In other words, if the melt index of the linear low density polyethylene is less than 25 g/10 minutes, the melt elasticity of the discharged yarn will increase and the spinability will be inferior to that of the linear low density polyethylene alone. And the melt index of linear low density polyethylene is 100.
g/10 minutes or more, the viscosity is too different and a uniform blend cannot be obtained. As a result, a serious defect occurs in that the discharged yarn breaks just below the nozzle.

For the above reasons, the melt index of the linear low density polyethylene is preferably in the range of 35 to 80 g/10 minutes, even more preferably in the range of 40 to 70 g/10 minutes. If the heat of fusion of the linear low-density polyethylene is less than 25 cal/g, the spinning properties will be poor.

The crystalline polypropylene suitable for use in the blend structure of the present invention is isotactic polypropylene, which is limited to a melt index of 20 g/10 minutes or less. This is because, if it is outside this range, it will not be blended uniformly with linear low density polyethylene. In other words, the polypropylene segment in the blending mechanism of both components is "
Due to "too much flow", the suction speed in the yarn spinning process decreases.

In order to obtain the structure according to the present invention, linear low density polyethylene and crystalline polypropylene may be blended together and then spun using conventional spinning equipment. However, the blend ratio of linear low-density polyethylene and crystalline polypropylene also has a large effect on high-speed suction properties. The speed cannot be increased. Also, if the amount of crystalline polypropylene is greater than the amount of linear low-density polyethylene (on the contrary, the spinning properties will be poor).

Furthermore, when comparing the yarn-spinning properties of linear low-density polyethylene replaced with high-density polyethylene or low-density polyethylene and blended structures with crystalline polypropylene, the suction speed was found to be either impossible or impossible to spin. can't be done at high speed either.

In the blending mechanism of the present invention, polypropylene is located as an island component in a sea component of linear low-density polyethylene with respect to the fiber cross section and axial direction. The size of the island component is largely responsible for the silk-spinning property. If the melt viscosities of both components are too close, a fairly small island component will result.

As a result, the melt elasticity becomes too high to withstand high-speed suction. On the other hand, if the difference is too large, the island component becomes too large and both components are discharged in a macroscopic shape, which similarly cannot withstand high-speed suction in the silk-spinning process.

In producing the blend structure of the present invention, the following considerations may be taken into consideration regarding the spinning temperature. By blending crystalline polypropylene with linear low-density polyethylene, high-speed suction is possible even at low spinning temperatures, and it is also possible to prevent staining of the spinneret, which has been a problem in the past.

Linear low-density polyethylene alone has a temperature of around 250°C, considering high-speed suction properties, while crystalline polypropylene alone has a temperature of 270°C.
The spinning temperature of the blend structure of the present invention is usually 200 to 250°C, and more preferably 210 to 250°C.
230°C is applied. Note that the cross-sectional shape of the fibers is not limited to a round shape, and may be an irregular shape having a slit or a hollow cross-section.

The nonwoven fabric made from the blend structure of the present invention has superior tensile strength and softness compared to linear low-density polyethylene alone or polypropylene alone, and has a good texture without any "sliminess" characteristic of polypropylene. have.

In order to obtain a nonwoven fabric from the blend structure according to the present invention, it is possible to obtain the nonwoven fabric by dividing the yarn spinning process and the web making process.
From the viewpoint of productivity, it is preferable to obtain it by a continuous process as described below.

The method is the so-called spunbond method, in which the blend structure of the present invention is opened by suction with a high-speed suction gun, deposited on a moving wire mesh to form a web, and then passed to an embossing roll where it is compressed and heated to form a nonwoven fabric. It's something you get.

(Example) Next, the present invention will be specifically explained using examples.

Example 1 Various types of polyethylene and polypropylene were prepared as shown in Table 1.

Table 1 (continued) (Note) In Table 1, linear low density polyethylene is
PE, low density polyethylene is shown as LDPE, and high density polyethylene is shown as HDPE. Further, polypropylene is indicated by PP.

Next, yarn spinning was carried out under the conditions shown in Table 2. A in the blend ratio column of high density polyethylene and polypropylene in Table 2
The alphabetical symbols of ~G correspond to the sample symbols in Table 1.

Table 2 For each sample, a spinneret with a hole diameter of 0.4φ and 80 holes was used, and the discharge rate per hole was 1.5 g/min.

Table 3 shows the evaluation results for yarn spinning properties, and Table 4 shows the evaluation results for yarn quality.

Table 3 Results of evaluation of silk-spinning properties (Note) ■ In Table 3, "impossible" means that silk-spinning is impossible.

■ The staining of the cap was determined by observing the surface of the cap 1 hour after discharging the thread.

■Evaluation of yarn breakage was based on the number of yarn breakages per hour.

Table 4 Results of yarn quality evaluation As is clear from Tables 1 to 4, high-performance blend structures of polyethylene and polypropylene have improved operability (
It can be seen that it cannot be obtained in any way outside the scope of the present invention.

For example, when the linear low-density polyethylene alone of Comparative Example Kan 1 is compared with the blended structure of Sample No. 3 according to the present invention, both are excellent in suction speed, yarn performance, and texture. However, NU of the example of the present invention has good reeling properties, but NU of the comparative example
LL has a lot of dirt on the base.

Thread breakage caused by this was observed. As for the blend ratio, if the polypropylene content exceeds 50% by weight as in Comparative Example List 5 and Comparative Example 1)h6, the spinning property deteriorates and the texture also becomes "slimy". Comparative example 1) h
8 and comparative example patient 9. Comparative Examples N1) and 2 are cases in which polyethylene or polypropylene having a melt index outside the range of the present invention is used.

Comparative Example 1) &lIO and Comparative Example mll are cases where low-density polyethylene and high-density polyethylene were used, and it can be seen that both have poor spinning properties.

Example 2 A blend of 75% by weight of linear low-density polyethylene and 25% by weight of crystalline polypropylene, with a spinning temperature of 220°C and a suction speed of 8800 m/min, as well as 1) 13 of Example 1.
The fibers were opened under suction under the same conditions as above and deposited on a moving wire mesh to form a web, which was then introduced to an embossing roll and subjected to compression and heat treatment to form a nonwoven fabric. The performance of the obtained nonwoven fabric was excellent, and the fabric had a very good feel. The performance of the nonwoven fabric is shown in Table 5.

The method of measuring the physical property values in Table 5 is as follows.

The tensile strength is determined by the strip method of JIS L-1096.

The maximum tensile strength of a test piece with a width of 30 mm and a length of 100 mm was measured.

Total hand indicates softness and is JIS L-
According to the hand-o-meter method of 1096, slot width 1
Measured at 0 mm.

(Effects of the Invention) The blended structure obtained by the present invention can be produced with good operability, and when made into a nonwoven fabric after spinning, the structure has excellent softness and texture, so it is particularly suitable for applications such as the lining of disposable diapers. A suitable nonwoven fabric is obtained.

Claims (1)

[Claims] (1) A linear low-density copolymer of ethylene and octene-1, containing substantially 1 to 15% by weight of octene-1, with a density of 0.900 to 0.940 g/cm^3, and a melt index of ASTM. It is measured by the method of D-1238 (E) of 25 to 100 g/10 minutes, and the heat of fusion is 25 ca.
Linear low density polyethylene consisting of l/g or more is 99-5
0% by weight and melt index is ASTM D-123
8(E), consisting of 1 to 50% by weight of crystalline polypropylene smaller than 20 g/10 minutes, as measured by the method of 8(E),
A blend structure characterized by being melt-spun.