JPH07286051A - Expansible sheet - Google Patents

Abstract

PURPOSE:To obtain an expansible sheet which comprises a specific thermoplastic elastomer and a thermoplastic polyolefin elastomer poorly compatible with each other and has an expansibility improved by stretching. CONSTITUTION:The expansible sheet which contains, as the essential components, a thermoplastic styrene-diene block copolymer elastomer and a thermoplastic polyolefin elastomer poorly compatible with each other and which has been stretched. The former elastomer is produced by using isoprene. butadiene, etc., as the diene component, isoprene being pref. for obtaining a mild expansibility, and a styrene-isoprene-styrene triblock copolymer is esp. pref. because of its low tack and compression set. The triblock copolymer pref. has a triblock content of 80-100%, esp. 100%, and an average mol.wt. of 100,000 or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretchable sheet used for a portion (gather) requiring elasticity such as cuffs of clothing, joints such as ankles and wrists, openings of bags and the like. It is about.

[0002]

2. Description of the Related Art Heretofore, for example, as a gather for clothes, a band rubber made by knitting a plurality of thin rubber cords with cotton has been used, and socks and gloves have been knitted with a thin rubber cord. However, since the rubber band is knitted with cotton, there is a problem that the band itself becomes thick and there is a feeling of strangeness, and there is a problem that the human body is left with imprints. Therefore, in addition to a thin rubber sheet, there is a demand for an elastic sheet that has a good texture and is inexpensive and soft and stretchable. However, an inexpensive natural rubber type rubber sheet is suitable for use by the hygiene method in terms of allergic sensitization. There is a problem, and when a rubber such as SBR or NBR that requires cross-linking is formed into a sheet, there is a problem that a thin sheet cannot be formed by a heating process for cross-linking. On the other hand, if a thermoplastic elastomer made of styrene / isoprene / styrene block copolymer is used, a soft sheet can be obtained, but there is a problem that tack exists, and a sticky feeling remains even if the sheet has a small tack. It had the drawback that you could only get a seat.

[0003]

Further, as an elastic tape, a thermoplastic elastic tape comprising a butadiene resin and / or a polyolefin resin and an aromatic vinyl compound-conjugated diene block copolymer has been proposed (Japanese Patent Laid-Open No. Sho 61-206). 5
9-155478 gazette), since such a tape is not stretched, there is a problem that the permanent strain is large and the tape is stretched by the first pulling upon use. further,
There was a problem that the tension of the first time and the tension of the second time were so different as to be noticeable in use.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and improves stretchability by stretching the sheet after extrusion to minimize permanent set. In addition, it is possible to eliminate the stickiness of the styrene / diene block copolymer, which is a drawback of the styrene / diene block copolymer, by mixing and dispersing a thermoplastic polyolefin elastomer with a small compatibility with the styrene / diene block copolymer. A highly elastic stretchable sheet having excellent properties can be obtained.

That is, according to the present invention, a thermoplastic elastomer comprising a styrene / diene block copolymer and a polyolefin thermoplastic elastomer having a low compatibility with the elastomer are essential components and stretched. Providing a sex sheet.

In the styrene / diene block copolymer used in the present invention, examples of the diene include isoprene and butadiene, and isoprene is preferable for soft stretchability, and particularly for reducing tackiness and permanent set. In particular, a triblock styrene / isoprene / styrene block copolymer (hereinafter referred to as SIS resin) is more preferable. Here, the triblock amount is 80 to 100%,
100% is particularly preferable. The average molecular weight is not particularly limited because it varies depending on the amount of diblock, amount of triblock, etc., but it is usually 100,000 or more.

The stretchable sheet of the present invention comprises the above-mentioned styrene
A thermoplastic elastomer composed of a diene block copolymer is mixed and dispersed with a thermoplastic polyolefin-based elastomer having a small compatibility with the thermoplastic elastomer. Here, “small compatibility” means a state in which the particles are microscopically non-uniformly mixed and a state in which they are uniformly dispersed in appearance. Appearance is transparent even if they are compatible with each other, and if the compatibility is low, it becomes translucent and whitened, while if they are not compatible, unevenness and lumps appear.

The polyolefin-based thermoplastic elastomer having a small compatibility may be one which is whitened or translucent when dispersed by mixing with the styrene / diene block copolymer, for example, an ethylene / propylene copolymer. , Ethylene / propylene / diene terpolymers, ethylene / 1-butene copolymers, ethylene / 1-butene diene terpolymers and the like.

The amount of these polyolefin-based thermoplastic elastomers added is not particularly limited as long as the tackiness can be reduced by dispersing these resins, but if it is too large, the permanent set becomes large, so that the polyolefin-based thermoplastic elastomer is added. In the case of, it is preferably 50% by weight or less, usually about 20 to 40% by weight. By dispersing these resins, the tackiness is lowered, the handleability is improved, the fusion of the sheets can be prevented when the sheets are wound, and the pearly texture can be provided.

The method of dispersion is not particularly limited, but mixing and dispersion of only a heating screw attached to the extruder is sufficient, and a masterbatch may be prepared in advance by a kneader.

In the present invention, the texture of the resulting sheet can be improved by adding a filler. Examples of such fillers include white fillers of calcium carbonate powder, barium sulfate powder, aluminum hydroxide powder, titanium oxide powder, and the like, or a mixture thereof. The average particle size of these fillers is preferably 0.1 to 10 μm, particularly preferably 1 to
When it is 3 μm and less than 0.1 μm, the effect of improving the texture is small, and when the amount of addition is large, the viscosity of the resin becomes extremely high and extrusion molding becomes difficult. On the other hand, if it exceeds 10 μm, the sheet surface becomes rough and the softness is lost, which is not preferable. The amount of addition depends on the hiding power of the filler, but is usually about 10 to 70% by weight, preferably 30 to
It is about 55% by weight. If it is less than 10% by weight, the degree of whitening due to stretching is small, and if it exceeds 70% by weight, the viscosity of the resin becomes high and extrusion molding becomes difficult, which is not preferable. Further, as other additives, for example, a lubricant, a heat stabilizer, an ultraviolet absorber and the like can be selectively added as required.

In the present invention, these resins can be formed into a sheet by extrusion molding. Extrusion is
T-type, inflation molding and the like can be used and are not particularly limited, but the die temperature is about 160 to 230 ° C, preferably about 180 to 210 ° C. If the temperature is too low, the pressure becomes high and extrusion becomes difficult, and if it is too high, the resin may deteriorate.

In the present invention, the stretchability of the sheet obtained above can be remarkably improved by stretching. The stretching method is not particularly limited as long as the stretchability of the sheet can be improved,
For example, in the case of roll stretching, the stretching ratio at room temperature is at least 1.5 times or more, preferably 2 times or more, and particularly preferably 2 to 5 times. The optimum range of such draw ratio is
Depending on various factors such as the resin composition and molecular weight,
If the stretching ratio is too small, uneven stretching may occur, and if it is too large, the sheet may be broken. Moreover, even if the number of times of stretching is once, the stretchability can be remarkably improved, and by repeating it several times, the permanent strain and the softness at the time of stretching can be improved.

Since the stretching temperature is not preferable near the melting point of the material to be used, it is preferably around the temperature actually used, that is, 40 ° C. or lower, and particularly when a resin having crystallinity is added, it is recrystallized to soften it. In consideration of the loss of water, the temperature is preferably about 10 to 30 ° C.

The obtained sheet thickness is preferably 5 to 300 μm from the viewpoint of ensuring soft stretchability.
In addition, especially considering economy, use and handleability,
100 μm is preferable. In addition, such an elastic sheet,
When it is used for clothing, the pressing force on the human body is important, and the thickness of the sheet, the width of the sheet used, the elastic modulus, etc. are related, but the 50% tensile stress of the sheet at room temperature is preferably 35 Kg / cm ² or less, especially 20 Kg / cm. ² or less is preferable.
Further, in actual use, the smaller the permanent set of tensile strength of the sheet, the more preferable. In the present invention, it is preferably 35% or less, particularly preferably 15% or less.

Further, the elastic sheet of the present invention can be made into a multi-layer such as 2 to 3 layers as a single sheet, and further, a non-woven fabric or a polyolefin-based material such as polyethylene or polypropylene for reinforcing the sheet and improving appearance. It is also possible to form a composite by laminating a polyurethane-based or polyester-based plastic film on at least one surface of the stretchable sheet. Examples of such non-woven fabric include spun-bonded or melt-blown non-woven fabric sheets of polyethylene, polypropylene, polyester or the like. To be used as an elastic body, the stretchable sheet is attached to the non-woven fabric in a state of being stretched by at least 25%. May be. The thickness of the non-woven fabric is not limited as long as the elasticity of the resulting composite sheet is not impaired, but the basis weight is preferably 50 g / m ² or less. Further, from the economical point of view, the filler may be mixed with a resin sheet of polyolefin type, polyurethane type or the like. In this case, the addition amount is 30 parts by weight or more, preferably 40 to 60 parts by weight. In order to form a composite with these resin sheets, the stretchable sheet can be attached in a stretched state as in the case of the non-woven fabric, or can be obtained by co-extrusion together with the sheet as long as the stretchability is not significantly deteriorated. . The thickness of such a resin sheet is preferably 50 μm or less, and more preferably 30 μm or less, because the elasticity decreases when the resin sheet is too thick.

The bonding method is not particularly limited as long as it can hold both sheets such as linear, dot-shaped, and planar sheets with an adhesive or a pressure-sensitive adhesive, and may be fused by heating.

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. In the table, parts indicate parts by weight. Examples 1 to 15 The elastic sheet of the present invention was prepared by the following method. Table 1
Further, each resin pellet and powder were heated and mixed by a biaxial kneading device based on the formulation shown in Table 2 and then an extruded sheet having a thickness of about 65 μm was prepared by an extrusion molding device (die temperature 210 ° C.). Then, it was stretched 3 times by a roll stretching device at 25 ° C. to a thickness of about 50 μm, and the sheet was wound in a substantially free state.
The mechanical properties of the obtained sheet were measured with a test piece slit to a width of 0 mm, and the results are shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

The components of Tables 1 and 2 are as follows. SIS resin A: styrene / isoprene / styrene block copolymer (styrene content 17%, weight average molecular weight 1
70,000, triblock amount about 100%) SIS resin B: styrene / isoprene / styrene block copolymer (styrene content 15%, weight average molecular weight 2)
SIS resin C: styrene / isoprene / styrene block copolymer (styrene content 16%, weight average molecular weight 1)
90,000, triblock amount about 70%) SBS resin A: styrene-butadiene-styrene block copolymer (styrene content 21%, weight average molecular weight 1
70,000, triblock amount about 80%) Polyolefin elastomer A: ethylene / propylene copolymer (ethylene content 80%, weight average molecular weight 2
70,000) Polyolefin elastomer B: ethylene / 1-butene / ethylidene norbornene copolymer (ethylene / butene molar ratio = 90/10, weight average molecular weight 170,000) Polyethylene: linear low density polyethylene (density 0.92
g / cm ³ ) Filler: Stearic acid surface-treated calcium carbonate powder (average particle size 1.8 μm) Although not shown in the table, 3% of an aliphatic amide wax as a lubricant and phenolic as a heat stabilizer 2% of stabilizer was added.

The mechanical properties of the film were measured at a room temperature of 23 ° C. using a universal tensile tester with a sample of 10 mm width × 100 mm length at a tensile speed of 300 mm / min. After the permanent set was held for 1 min in the state of 100% extension, the tension was released and the residual extension was measured. In the table, the sheet flow direction is MD and the width direction is TD. The tensile modulus was calculated by the stress at 50% elongation in consideration of practicality.

The tack property was evaluated using the tack test measuring device according to the following criteria. ◎: 1 g or less ○: 2 g or less △: Less than 5 g ×: 5 g or more

The blocking was evaluated by the presence or absence of breakage of the sheet when the sheet was wound around a roll and then rewound.

Examples 16 to 21 Stretchable sheets were prepared in the same manner as in Example 1 by changing the stretching conditions as shown in Table 3 according to the composition of Example 1 and evaluated in the same manner, and the results are shown in Table 3.

[0026]

[Table 3]

Example 22 The stretchable sheet prepared in Example 1 was stretched 100%, and a polypropylene non-woven fabric (weight per unit area: 18 g / m ² ) was attached thereto by a roll laminator. For the bonding, a styrene-based pressure-sensitive adhesive linearly applied by spraying was used.
These composite stretchable sheets were similarly evaluated, and the results are shown in Table 4.

[0028]

[Table 4]

Example 23 A non-woven fabric of polypropylene (weight per unit area: 35 g / m ² ) was laminated with a roll laminator in a state where the stretchable sheet prepared in Example 1 was stretched 100%. For the bonding, a styrene-based pressure-sensitive adhesive linearly applied by spraying was used.
These composite stretchable sheets were similarly evaluated, and the results are shown in Table 4.

Example 24 The same polyethylene as in Example 9 and the same filler as in Example 14 were mixed in a biaxial kneader to prepare masterbatch pellets. An extruded sheet was prepared from the resin and the compounded resin of Example 15 by a two-layer extrusion molding apparatus so that the thickness ratio was 1: 5, stretched in the same manner as in Example 1, and each property was evaluated. The results are shown in Table 4.

Comparative Examples 1 to 8 After the sheet was prepared in the same manner as in Example 1 with the formulations shown in Table 5, each property was measured, and the results are also shown in Table 5.

[0032]

[Table 5]

Comparative Example 9 A sheet was prepared in the same manner as in Example 1 except that it was not stretched according to the composition shown in Table 5, and each property was measured. As a result, the permanent set was about 1.7 although it varied depending on the composition. Twice as much, the tensile modulus increased by about 25%.

As can be seen from these examples, according to the present invention, a soft stretchable sheet was obtained. All of these sheets had a translucent pearly texture. Here, regarding the elastic modulus, for example, a stress of 10 kg /
If it is cm ² , a tape having a width of 10 mm and a thickness of 50 μm can produce a rubber which can be stretched with a force of 50 g at 50% elongation. Looking at their elastic moduli in the table, they are 4 to 36 Kg / cm ² , and the permanent set is also 7 to 26%. Regarding the growth,
Although the value is low in the system with elastomer B added,
It is considered that this is because the polyethylene component in the elastomer B is crystallized by stretching and retains the length, has higher orientation, and the strength in the TD direction is relatively lower than that in the MD direction.

Regarding tackiness, polyethylene and SI
Although the system of S resin C (triblock amount 70%) was slightly inferior, blocking did not occur. Further, in the system to which calcium carbonate was added, the elastic modulus tended to be lower than in the system to which calcium carbonate was not added. With regard to the number of times of stretching, the elastic modulus decreased by about 13% at one time. In reality, a large decrease does not occur after four times, and it is considered that the value will be about 60% of the initial value. Regarding the stretching temperature and the stretching rate, no size difference was obtained.

On the other hand, in Comparative Examples, soft rubbers could be prepared in systems other than polyethylene, but blocking occurred in all cases. Further, the obtained sheet had a rubber gloss. In a system containing a large amount of polyethylene, although the blocking does not occur, the elastic modulus is 100.
It was larger than Kg / cm ² , and the permanent set was large, and it could not be said to be an elastic sheet. In addition, calcium carbonate 7
Comparative Example 6 containing 0% or more had a high viscosity and could not be extruded.

[0037]

The stretchable sheet of the present invention has soft stretchability, and its tension does not increase much even when stretched.
It has advantages such as wide use and no discomfort. In addition, a sheet obtained by laminating a support such as a nonwoven fabric on such a sheet also has an advantage that the tension at the time of tension before shrinkage can be increased and the dimension stability in automation is extremely excellent.

Front page continuation (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B32B 7/02 9268-4F 25/10 27/32 Z 8115-4F 27/40 7421-4F C08L 9/06 LBG 23/00 LCB LCN 53/02 LLY // B29K 9:00 B29L 9:00 (72) Inventor Katsumi Hori 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (4)

[Claims] 1. A stretchable sheet comprising a thermoplastic elastomer comprising a styrene / diene block copolymer and a polyolefin thermoplastic elastomer having a low compatibility with the elastomer as an essential component and stretched. 2. The stretchable sheet according to claim 1, wherein the styrene / diene block copolymer is a styrene / isoprene / styrene block copolymer, and the triblock amount thereof is 80 to 100%. 3. A stretchable sheet obtained by laminating a nonwoven fabric on at least one surface of the stretchable sheet according to claim 1. 4. A stretchable sheet obtained by laminating a plastic sheet containing a polyolefin-based or polyurethane-based resin in an amount of 30 parts by weight or more of a filler on at least one surface of the stretchable sheet according to claim 1.