JPH05200860A - Heat-resistant bag - Google Patents

Abstract

PURPOSE:To provide a heat-resistant bag especially suitable as a bag for high temp. sterilizing treatment having not only excellent heat resistance and excellent transparency but also film strength and seal strength. CONSTITUTION:A heat-resistant bag is composed of a biaxially stretched and thermally fixed polybutylene terephthalate film with intrinsic viscosity of 0.7 or more and the degree of surface orientation of 0.07-0.18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant bag which is particularly suitable as a storage bag for heat sterilizing industrial waste.

[0002]

2. Description of the Related Art In recent years, used equipment, residue, waste such as waste discharged from hospitals or various research institutions are
In order to prevent secondary pollution by them, heat sterilization and landfill disposal are often used.

By the way, when these industrial wastes are heat-sterilized, a method is used in which the wastes are first stored in a bag and then the bag is heated to a temperature of about 120 ° C. or higher. When a bag made of polyolefin such as polypropylene is used, there is a problem that the heating temperature is limited due to the problem of heat resistance and that sterilization requires a long time.

Therefore, in order to improve such an inconvenience in work efficiency due to insufficient heat resistance, a method of using a bag made of biaxially stretched polyethylene terephthalate has been studied. As is well known, polyethylene terephthalate is heat-sealed. Since it is poor in properties, it is difficult to make a bag with a single film, and mechanical strength such as impact and tear is insufficient, and it is easy to break the bag. Therefore, it cannot be used as a bag of this kind.

On the other hand, JP-A-2-242744 proposes a heat-resistant bag using a polybutylene terephthalate film. The bag described in the publication is a tubular shape manufactured by a normal inflation method. Since it is a bag made of the film of, the film has excellent heat resistance, but the transparency of the film is lost due to the whitening phenomenon in the inflation molding process based on the extremely fast crystallization unique to polybutylene terephthalate, and most of it is accompanied by molecular orientation. In this case, the heat-resistant bag is not satisfactory either, because the film strength such as tension and impact is fragile and there are many problems that the seal end portion is easily torn.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is a high temperature sterilization treatment having excellent heat resistance and transparency, film strength, seal strength and the like. The point is to provide a heat-resistant bag that is particularly suitable as a bag for use.

[0007]

Means for Solving the Problems As a result of comprehensive investigations of various heat-resistant resins in order to achieve the above-mentioned objects, specific film characteristics, moldability, economical efficiency, etc. Focusing on the fact that the biaxially stretched polybutylene terephthalate film under specific conditions is transparent and has both excellent mechanical strength such as tensile and impact and sealing strength based on its unique crystal structure, and the specific film. The bag made with is 180 for a short time within 1 hour.
The present invention has been completed by finding that sufficient durability can be maintained even in an atmosphere with a temperature as high as 0 ° C.

That is, the present invention has an intrinsic viscosity of 0.7 or more,
In addition, the present invention relates to a heat-resistant bag comprising a polybutylene terephthalate film having a degree of plane orientation of 0.07 to 0.18 and heat-fixed.

The heat-resistant bag of the present invention will be described in detail below.

In the present invention, polybutylene terephthalate means a polyester having butylene terephthalate as a main repeating unit, and specifically, 1,4-butanediol as a glycol component and terephthalic acid as a dibasic acid component or It is a polyester obtained by condensation with the lower alcohol ester.

Further, in the present invention, a copolyester mainly composed of such polybutylene terephthalate may be used, and in this case, there is an advantage that the sealing strength becomes strong although the heat resistance is slightly lowered. Here, the copolyester mainly composed of polybutylene terephthalate means that a part of terephthalic acid or a lower alcohol ester thereof as a dibasic acid component may be replaced with other parts such as isophthalic acid, phthalic acid,
Adipic acid, sebacic acid, or the like, and / or 1,4-butanediol as a glycol component is partially replaced with other dibasic acid such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, cyclohexane dimethanol. A polyester obtained by condensing a substitute of glycol such as.

The heat-resistant bag of the present invention uses the above polybutylene terephthalate having an intrinsic viscosity of 0.7 or more, preferably 0.8 or more.

Here, the intrinsic viscosity is a value measured at 25 ° C. in orthochlorophenol, but in the case of polybutylene terephthalate, the meaning of this intrinsic viscosity is not limited to the viscous concept but to the crystallization rate. Is also an important factor that influences the whitening phenomenon of unstretched films.
Therefore, when the intrinsic viscosity is less than 0.7, the melt viscosity is low and drawdown easily occurs, and it becomes difficult to maintain the shape at the time of extrusion, and the crystallization speed becomes remarkably high. However, the whitening phenomenon due to the formation of spherulites cannot be suppressed and the transparency is impaired, and the film strength such as tensile strength and impact strength, and the seal strength also decrease. There is no particular upper limit to the intrinsic viscosity, but if it is too high, the resin pressure at the time of extrusion will be high, and productivity will be reduced, and the thickness of the resulting film will be large.
The following is preferable.

It should be noted that the polybutylene terephthalate of the present invention may contain a small amount of other polyesters, polycarbonates and the like within a range that does not impair the properties thereof, and further, if necessary, an appropriate lubricant, anti-blocking agent, Additives such as an inorganic extender, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a plasticizer, a coloring agent, a crystallization inhibitor, and a crystallization accelerator may be added.

The heat-resistant bag of the present invention also comprises the above polybutylene terephthalate having a degree of plane orientation of 0.07 to 0.18,
It is preferably composed of a film biaxially stretched and heat-set so as to have a thickness of 0.10 to 0.16.

In the present invention, the effect obtained by constructing the heat-resistant bag with the polybutylene terephthalate film having such a specific plane orientation is superior in transparency as compared with the above-mentioned bag made of the conventional inflation film. Of course, tension due to molecular orientation during stretching,
Both mechanical strength such as impact and seal strength can be greatly improved.

Here, the plane orientation degree ΔP is the refractive index in the length direction, width direction and thickness direction in the plane of the film, respectively.
When x, Ny, and Nz, ΔP = (Nx + Ny) / 2
-Nz. If the degree of plane orientation is less than 0.07, the thickness is large due to insufficient stretching, the transparency is poor, and sufficient strength is obtained in terms of film strength such as tension and impact. I can't get it. On the other hand, when the plane orientation degree is larger than 0.18, it is necessary to stretch at a high magnification, so that the transparency is lost when the film is made thick, and the elongation becomes small when the transparency is improved. It becomes difficult to achieve both transparency and film strength, such as a decrease in strength such as impact and tear.

In order to produce the polybutylene terephthalate film of the present invention, the polybutylene terephthalate raw material having the above-mentioned intrinsic viscosity is melt-extruded at a temperature of 240 to 290 ° C., and then rapidly cooled at a temperature of 30 ° C. or less to be transparent. It is obtained by a series of methods of forming an unstretched film, followed by a biaxial stretching and heat setting through a preheating step of 40 ° C. or less. At this time, the biaxial stretching method may be any method such as sequential or simultaneous biaxial stretching method using a tenter, tubular simultaneous biaxial stretching method,
In the case of a resin having a high crystallization rate such as polybutylene terephthalate, the stretching rate is fast, and moreover, the tubular stretching method in which the stretching is carried out simultaneously in the longitudinal and lateral directions suppresses the oriented crystallization in the stretching process, and the uniform and stable stretching is possible. preferable.

Specific examples of the stretching conditions in the tubular simultaneous biaxial stretching method include a stretching zone designed such that the time from the start to the end of stretching is within 3 seconds, the thickness of the unstretched film and crystallization. 60 to 14 depending on the degree
Stretching is performed under the conditions of 0 ° C. and a magnification of 1.5 to 4.0 times so that the degree of plane orientation becomes 0.07 to 0.18. It is also important to maintain the preheating temperature of 40 ° C. or lower. If the preheating temperature is higher than 40 ° C., stretching in the machine and transverse directions becomes unbalanced, and uniform stretching becomes difficult.

The heat setting conditions for producing the polybutylene terephthalate film in the present invention include:
When the temperature is low, the heat shrinkage rate of the film is large, and conversely, when it is too high, the molecular orientation is lowered and the above-mentioned degree of plane orientation cannot be maintained. Therefore, when the melting point of polybutylene terephthalate is Tm, (Tm- 80) to (Tm-10)
It is preferable to heat-set at a temperature of ° C and under a tension or a relaxation rate of 40% or less.

The heat-resistant bag of the present invention is manufactured by sealing the biaxially stretched and heat-fixed polybutylene terephthalate film into a bag shape. The fusing seal is stronger than the bar seal, and it is preferable in terms of appearance that there is less whitening of the seal portion as seen in the heat bar seal.

When the heat-resistant bag of the present invention is used as a bag for sterilization of industrial waste, the waste leaks from the bag as needed for the purpose of increasing the thermal efficiency and shortening the processing time. It is also possible to perforate the bag with a hole having a diameter of 0.1 to 50 mm, which is not enough. The thickness of the polybutylene terephthalate film constituting the heat-resistant bag of the present invention varies depending on the purpose of use, but is usually 10 to 1
00μ, preferably 20 to 70μ, more preferably 2
About 5 to 50 μm is preferable in view of durability such as film strength and seal strength, moldability, and economical efficiency.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto.

The methods of measuring and evaluating the physical properties used in the present invention are as follows. (1) Intrinsic viscosity Measured in orthochlorophenol at 25 ° C. (2) Degree of plane orientation It was calculated as ΔP from the refractive indexes in the length direction, width direction and thickness direction in the film plane. The refractive index was measured using an Appe refractometer manufactured by Atago Co., Ltd. under a sodium light source. (3) Melting point of film (unit: ° C) Differential scanning calorimeter DSC22 manufactured by Seiko Instruments Inc.
It was determined from the crystal melting peak when the sample was heated at 0 ° C. at a temperature rising rate of 20 ° C./min. (4) Tensile strength (unit: Kg / mm2) The tensile strength was measured by a method according to JIS C2318. (5) Impact strength (unit: Kg-cm) Using a pendulum impact tester (Film Impact Tester, manufactured by Toyo Seiki Seisaku-sho, Ltd.), the impact head was measured under 1/2 inch and full scale of 30 Kg-cm. (6) Sealing strength (unit: g / 10 mm) After sealing two films in a state of being overlapped with each other with a fusing sealing machine (PSC-310E manufactured by Fuji Manufacturing Co., Ltd.), peel strength of the sealing portion was measured. (7) Transparency According to JIS K6741, haze was measured with a digital turbidimeter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.
As for transparency, the haze measured is less than 5% (○),
5% or more and less than 10% were evaluated as (Δ), and 10% or more were evaluated as (x).

Example 1 A polybutylene terephthalate raw material (“Duranex” manufactured by Polyplastics Co., Ltd.) having an intrinsic viscosity of 1.4, which comprises terephthalic acid as a dibasic acid component and 1,4-butanediol as a glycol component, is used as the tip. Using an extruder with a 65 mm caliber equipped with a circular die, screw rotation speed 40 rpm, cylinder and die temperature 240 to 28
After melt-extruding at 0 ° C., it was immediately water-cooled at a temperature of 5 ° C. to obtain a tubular unstretched film having a folded diameter of about 170 mm and a thickness of about 200 μ. While preheating this unstretched film at a temperature of 20 ° C., it is guided to a pair of upper and lower nip rolls having different peripheral speeds, and pressurized air is fed at a stretching temperature of 80 to 110 ° C. to obtain a stretching ratio of 2.5 times in each length and width. Tubular simultaneous biaxial stretching was performed. While still maintaining the tube shape, heat-fixing at 200 ° C for 3 seconds while giving a relaxation of about 5%, the thickness is 35μ, and the folding diameter is about 400m.
m, a tubular biaxially stretched film having a plane orientation of 0.14 was produced. About 60 of the tubular film thus obtained
A heat resistant bag was produced by cutting at a length pitch of 0 mm and fusing and sealing one end thereof. The physical properties of this heat resistant bag are shown in Table 1.

Comparative Example 1 Using the same polybutylene terephthalate raw material as in Example 1 above, a tubular film having a thickness of 35 μ and a folded diameter of about 400 mm was produced by an inflation molding method. The tubular film is cut at a length pitch of about 600 mm, and one end of the film is fused and sealed.
It was shown to.

Comparative Example 2 A bag was produced in the same manner as in Example 1 using a commercially available biaxially oriented polypropylene film having a thickness of 35 μm. The physical properties of the bag are shown in Table 1.

[0028]

[Table 1]

From the results shown in Table 1, the heat-resistant bag made of the biaxially stretched and heat-fixed polybutylene terephthalate film of the present invention uses the polybutylene terephthalate film and the biaxially stretched polypropylene film produced by the conventional inflation molding method. Heat resistance, transparency, compared to bags
The film strength and seal strength were all excellent.

Examples 2 to 4 and Comparative Example 3 A heat resistant bag was produced in the same manner as in Example 1 except that polybutylene terephthalate raw materials (“Duranex” manufactured by Polyplastics Co., Ltd.) having different intrinsic viscosities were used. did. The physical properties of this heat-resistant bag are shown in Table 2. The polybutylene terephthalate having an intrinsic viscosity outside the range of the present invention had poor transparency and poor film strength such as tensile strength and impact strength.

[0031]

[Table 2] In the table, “IV of PBT” indicates the intrinsic viscosity of the polybutylene terephthalate raw material to be tested, and “ΔP” indicates the degree of plane orientation.

Examples 5-8, Comparative Examples 4-5 Example 3 except that the screw rotation speed during melt extrusion was changed.
With a diameter of about 170 mm and a thickness of about 6
Various tubular unstretched films having different thicknesses of 0, 90, 140, 180, 290 and 480μ were produced. While preheating this unstretched film at a temperature of 20 ° C., it is guided to a pair of upper and lower nip rolls having different peripheral speeds and stretched at a temperature of 80 to 130.
C., and the stretching ratio is 1.4 in the vertical and horizontal directions from the ascending order of the thickness of the unstretched film.
Tubular simultaneous biaxial stretching was performed so as to obtain a magnification of 8, 2.2, 2.5, 3.2, 4.1. Continue to maintain the tube shape while giving about 5% relaxation and 180-210 ℃
The thickness of 30μ is fixed by heat setting for 3 seconds.
The degree of plane orientation varies from 0.06 to 0.19. 6
Two types of tubular biaxially stretched films were produced. Physical properties of a bag produced by cutting these tubular films at a pitch of about 600 mm and fusing and sealing one end thereof are shown in Table 3.
It was shown to. From the table, it can be seen that all of those having a degree of plane orientation out of the range of the present invention have poor transparency, and in particular, the degree of plane orientation is 0.07.
Those of less than were also inferior in film strength.

[0033]

[Table 3] “IV of PBT” and “ΔP” in the table are the same as in the case of Table 2 above.

[0034]

As described above, the heat-resistant bag of the present invention is composed of a film obtained by biaxially stretching and heat-fixing polybutylene terephthalate having a specific intrinsic viscosity so that the degree of plane orientation becomes 0.07 to 0.18. Therefore, it has much higher heat resistance than conventional polyolefin bags, and also has excellent transparency and film strength not found in bags using the polybutylene terephthalate film produced by inflation molding. It also has sealing strength.

Since the heat-resistant bag of the present invention can withstand a temperature of 180 ° C. for a short time within 1 hour, it is particularly suitable as a bag for heat sterilization treatment of industrial waste, which improves the efficiency of treatment work. It greatly contributes to.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area B29L 7:00 4F

Claims (3)

[Claims] 1. A heat-resistant bag comprising a polybutylene terephthalate film having an intrinsic viscosity of 0.7 or more and a degree of plane orientation of 0.07 to 0.18, which is heat-fixed and biaxially stretched. 2. The heat-resistant bag according to claim 1, wherein the polybutylene terephthalate film is simultaneously biaxially stretched by a tubular method. 3. The heat resistant bag according to claim 1 or 2, wherein the bag is a bag for sterilizing industrial waste.