JPS6345027A - Manufacture of polyoxymethylene tape - Google Patents

Abstract

PURPOSE:To possess excellent mechanical characteristics such as the high modulus of elasticity and high strength and to reduce unevenness in thickness widthward, by a method wherein stretching where stretching stress (sigmaD) on and after the second stage satisfies a fixed constituent necessary matter to stretching magnification (lambda) is performed. CONSTITUTION:A unstretched tape 2 of polyoxymethylene would round a wind-up drum 1 of the unstretched material is drawn out into the first stage stretching zone by a drawing-out machine 3. A temperature rise of the same within the first stage induction heating furnace 5 is performed, the first stage stretching is performed immediately, and simultaneously with taking off of the same firstly the same is sent out to the second stage stretching zone. A temperature rise of the same is made within the second stage induction heating furnace 7 and outside heating furnace 8 and the second stage stretching is performed. Stretching shall be such that stretching stress (sigmaD) on and after the second stage satisfies sigmaD>0.78lambda+10.1 to stretching magnification (lambda), where lambda=lambda1Xlambda2X...Xlambdan, lambdan: the n-th stage stretching magnification sigmaD=(alpha2+alpha3+...+alphan)/(n-1), and sigman: the n-th stage stretching stress (kg/mm<2>).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing polyoxymethylene tape. More specifically, the present invention relates to a method for obtaining a stretched polyoxymethylene tape having high elastic modulus, high strength, and small thickness unevenness in the width direction.

(Prior art) Obtained by melt molding. 1? When a tape-shaped unstretched body of lyoxymethylene is superstretched, it becomes a t-polymer material having high elastic modulus and high strength and suitable for industrial materials.

A method of producing a stretched polyoxymethylene tape having such high physical properties by stretching is already known. For example, JP-A-60-220730 discloses rC stretching an unstretched polyoxymethylene tape by 30 times or more.

Furthermore, in the 7,300-page proceedings of the 1981 National Conference of the Institute of Electrical Communication Engineers, an unstretched polyoxymethylene tape with a width of 15" and a thickness of 0.5 fi was heated using a dielectric heating method, and the stretching ratio was 28 times. It is shown that a stretched product having a tensile modulus of elasticity of 50 GPa or more was obtained.

(Problems to be Solved by the Invention) Since the stretched polyoxymethylene tape is used as an industrial material, K not only has excellent mechanical properties such as high elastic modulus and high strength, but also has uniformity in the shape of the tape. sexuality is required. In particular, there are strict requirements regarding thickness unevenness in the width direction of a stretched tape body, and in order to improve mechanical properties, it is difficult to satisfy thickness uniformity simply by increasing the stretching ratio. Furthermore, if the film is stretched with large thickness irregularities, defects such as warping and cracking may occur, making it impossible to use it as an industrial material. Furthermore, when the stretched tape is used by slitting it at a constant width, it goes without saying that if the thickness is uneven, the utilization rate in the width direction will be low and it will be extremely uneconomical.

An object of the present invention is to provide a method for obtaining a stretched polyoxymethylene tape having excellent mechanical properties such as high elastic modulus and high strength, and having small thickness unevenness in the width direction.

(Preliminary measure to solve the problem) In order to achieve the above-mentioned purpose, the present inventors have investigated the mechanism of super-stretching a tape-shaped unstretched body made of polyoxymethylene in multiple stages and the stretching ratio. After intensive research and consideration from both sides of stretching stress, we found that when stretching is carried out in which both conditions satisfy a specific relationship, it has excellent mechanical properties such as high elastic modulus and high strength, and has small thickness unevenness in the width direction. It has been discovered that a stretched polyoxymethylene tape can be obtained, and the present invention has been achieved.

That is, the present invention provides a method for manufacturing a tape by stretching an unstretched tape-like body made of polyoxymethylene in multiple stages, in which the stretching stress (σD) in the second and subsequent stages is adjusted to the stretching ratio (λ).
) is subjected to stretching that satisfies the following formula.

σD>0.78λ+10.1 However, λ=λ1×λ2×...Xλyu λn: nth leg 0
Stretching ratio The stretching ratio (λ) and stretching stress (σD) are calculated by the following formula.

Cross-sectional area of the fourth stage stretched body Wo/Lo・ρO Wt/LI・ρl Ln: sample length (cm ), Wn: sample type t (,9),
ρn=sample density determined from density gradient tube method (,9/evN
) Tn: nth stage stretching tension (2) The present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing an embodiment of a stretching apparatus in the case of two-stage stretching. The device shown in Fig. 1 consists of a feeding machine 3 consisting of a pair of non-nip rolls &, 1' and a pair of nip rolls b.
, b' and the first drawing machine 6, which performs the first stage of stretching using the speed ratio of both, and the first drawing machine 6 and the nip roll e, and a second-stage stretching zone in which the second-stage stretching is performed using the speed ratio between the two drawing machines 10 and the second drawing machine 10 consisting of O'. The first pulling machine 6 corresponds to a tension separating device, and the tension of the stretched body is independently controlled on both sides thereof. In FIG. 1, a polyoxymethylene tape-shaped unstretched body 2 wound around an unstretched body winding drum 1 is fed out to a first-stage stretching zone by a feeding machine 3, and heated in a first-stage dielectric heating furnace S. The film is then immediately subjected to first-stage stretching, that is, neck stretching, and is taken up by a first pulling machine, which is a tension separation device, and at the same time sent to a first and second-stage stretching zone. The temperature is raised in the second stage dielectric heating furnace 7 and the external heating furnace 8, and second stage stretching is performed.

Subsequently, the stretched body 11 is taken up by a second take-up machine 10, and then wound up by a wind-up machine 12. In the figure, 4 and 9 indicate the first and second stage tension detectors, respectively.

The stretching in the present invention refers to the stretching stress (σD
) is relative to the stretching ratio (λ), σD)0.78λ+10
．． The stretching must satisfy 1. In super-stretching, which stretches from 7 times to 30 times, there is a two-stage stretching mechanism, the first stage being neck stretching in which the cross-sectional area of the unstretched body rapidly decreases; is a mechanism in which the cross-sectional area of the stretched neck body gradually decreases.

When an unstretched tape-like body is neck-stretched, a so-called neck-in phenomenon occurs, and both ends of the tape are thick at the edge height. In neck stretching, it is extremely difficult to eliminate this edge height by changing the stretching stress and stretching ratio. When the stretching stress and stretching ratio are decreased, the slope of the ear height becomes more pronounced9.
On the contrary, if both of them are increased, the tendency for edge height is slightly reduced, but the stretchability is reduced in the second stage of stretching. However, when super-stretching is performed in multiple stages, the second stage of stretching is performed in the second and subsequent stages, and a stretching stress of a certain value or more is applied at a predetermined stretching ratio. By gradually decreasing the thickness, it is possible to reduce the thickness unevenness. Furthermore, since the film is stretched with a stretching stress greater than a certain value relative to the stretching ratio, it is also possible to simultaneously improve mechanical properties such as tensile modulus and tensile strength. Same, Enll
When setting the 1lI stress to a value equal to or higher than the certain value expressed by the above formula, it is natural that there is a certain limit because if the stretching stress is too high, the film will break. In the case of an unstretched polyoxymethylene tape, it may break at σD) 0.78λ+30.

The stretching stress can be adjusted by adjusting the stretching temperature.

Further, the number of stretching stages is particularly preferably two-stage stretching or three-stage stretching, considering the cost and operability of the equipment.

The heating means used during stretching is not limited, and may include external heating,
For example, dielectric heating methods can also be used in addition to methods such as hot air, heating medium exposure method, hot plate, hot oval contact method, and infrared irradiation method.

The polyoxymethylene used in the present invention is a polyoxymethylene homopolymer 17t is a copolymer, and these include various additives for modifying polyoxymethylene,
For example, heat stabilizers, weatherability improvers, antistatic agents, plasticizers, etc. can be added.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

The measurement method in the same example is as follows.

Thickness determination: Using a thickness measuring device, measure the thickness at 10 points at equal intervals in the width direction of the sample. The average of the measured values at 10 points is taken as the thickness of the sample. The thickness and thickness unevenness are expressed as a percentage using the formula below.

(Thickness average value) and (Thickness average value) Tensile modulus: Tensilon was measured with a tensile tester using a differential transformer type elongation detector, and the elongation was within the range of 0.4 from the elongation-load curve. Find the initial elastic modulus (tensile speed 5 w/hiro)
.

The cross-sectional area of the sample is the weight (Wsg) of the sample and the length 25
cm), the density determined by the density gradient tube method (ρ39/e
The value calculated from x & ) using the following formula is used.

25・ρ3 Tensile strength: Measure the load at tensile break using the same testing machine used to measure the tensile modulus. (Tension speed 100ml/m). The cross-sectional area of the stretched body is the same as above.

Example 1 A tape-shaped unstretched body of polyoxymethylene (Tenatsuku (registered trademark) 3010 manufactured by Asahi Kasei Kogyo @) having a width of 50xx and a thickness of IJ was prepared using the two-stage stretching apparatus shown in FIG. 1 under the conditions shown in Table 1. It was stretched with Hot air at 175°C and 170°C is circulated in the first stage dielectric heating furnace and the second stage dielectric heating furnace, respectively. The stretching ratio in the 1ζ first stage stretching zone was 10 times.

FIG. 2 shows the relationship between the stretching ratio and the stretching stress, which satisfied the constituent requirement of the present invention σD)0.78λ+10.1. Table 2 shows the mechanical properties and thickness of the obtained telestretched body. It can be seen that all stretched bodies have small thickness unevenness and excellent mechanical properties.

Table 1 and following margins Table 2 Comparative Example 1 The same unstretched polyoxymethylene tape as in Example 1,
Stretching was carried out using a stretching device under the same conditions except that hot air from the second stage dielectric heating furnace was circulated at 180° C. and the temperature of the external heating furnace was set at 170° C. The result is the third
Shown in the table. In addition, the results are illustrated in Figure 2, and σ
D) 0.78λ+10.1 is not satisfied, and it can be seen from Table 3 that the thickness unevenness is significant.

Table 3 Example 2 Width 50g made of the same polyoxymethylene as Example 1,
A tape-shaped unstretched body having a thickness of 1.2 fl was stretched using the same stretching apparatus as in Example 1 under the conditions shown in Table 4. 1st
The stage dielectric furnace and the second stage dielectric furnace were heated at 175°C and 17°C, respectively.
Hot air at 0°C was circulated.

As shown in FIG. 2, which shows the relationship between the stretching ratio and the stretching stress, it can be seen that σD)0.78λ+10.1 was satisfied. The mechanical properties and thickness of the obtained specific stretched body were
As shown in the table, it can be seen that the thickness unevenness is small and the mechanical properties are excellent.

Fourth! ! Table 5 Comparative Example 2 Using the same unstretched polyoxymethylene tape and stretching equipment as in Example 2, the hot air of the second stage dielectric heating furnace was circulated at 180°C, and the temperature of the external 7yO heating furnace was Stretching was carried out under the same conditions except that the temperature was set at 170°C. The results are shown in Table 6. Also, as shown in Figure 2, the results are as follows:
σ, )0.78λ+10.1, and the sixth
It can be seen from the table that the thickness unevenness is significant.

Table 6 (Effects of the Invention) According to the present invention, polyoxylate 7 has excellent mechanical properties such as high elastic modulus and high strength, and has small thickness unevenness in the width direction.
A stretched methylene tape can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a stretching device showing an embodiment of the present invention;
FIG. 2 is a diagram showing the relationship between the stretching ratio λ and the stretching stress σD when stretching an unstretched polyoxymethylene tape having a width of 50 fl, a thickness of 1.0 fi, and a thickness of 1.2 mm. 1: unstretched body winding drum, 2: unstretched body, 3: feeding machine,
4: 1st stage tension detector, 5: 1st stage dielectric heating furnace, 6: 1st pulling machine, 7: 2nd stage dielectric heating furnace, 8: External heating furnace, 9
: 2nd stage tension detector, 1o: 2nd take-up machine, 11: Stretched body, 12: Winder Patent applicant Asahi Kasei Industries, Ltd. Figure 2

Claims (1)

[Claims] In a method for producing a tape by stretching a tape-shaped unstretched body made of polyoxymethylene in multiple stages, the stretching stress (σD) in the second and subsequent stages is as follows with respect to the stretching ratio (λ): A method for manufacturing a polyoxymethylene tape characterized by performing stretching that satisfies the following formula σD>0.78λ+10.1 However, λ=λ_1×λ_2×...×λ_n λ_n: Nth stage stretching ratio; σD=(σ_2+σ_3+...+σ_n)/(n-1
) σ_n: Nth stage stretching stress (Kg/mm^2)