WO2008154777A1 - A method for preparing a torsion film of polystyrene - Google Patents

Abstract

A method for preparing a torsion film of polystyrene comprises following steps: A. 60-97wt% polystyrene resin, HIPS resin, or at least one kind of modified polystyrene resin, 1-10wt% toughener, and 0-30wt% recycled materials are melted and plasticized in one or more extruders, extruded to form a single layer or coextrusion multi-layer film, and the film is set at 45-90°C by rapid cooling; B. the film is pre-heated at 100-140°C and stretched 1.5-5 fold longitudinally, and set at 60-95°C; C. the film stretched longitudinally is pre-heated at 110-140°C and stretched 3-6 fold transversely, set at 70-90 °C, trimmed, subjected to corona treatment and wound, wherein the polystyrene has a melt flow index of 0.6-5g/10min and a Vicat softening temperature of 102-108°C, the toughener is one or more selected from the group consisting of styrene-cis-butadiene copolymer, styrene-isoprene copolymer, styrene-cis-butadiene-acrylonitrile and blend composition of polystyrene - poly (cis-butadiene), and the recycled materials is scraps of the above films.

Description

 Polystyrene twisted film manufacturing method

Technical field

 The present invention relates to a method of producing a packaging material, and more particularly to a method of producing a non-resilient polystyrene twisted film for food packaging. Background technique

 The kink film used in food packaging is currently PVC twisted film, cellophane and PET twisted film. PVC twisted film has good chemical stability, is not easily corroded by acid and alkali, but is unstable to light and heat, and is easily exposed to light, heat, especially ultraviolet light to release hydrogen chloride and precipitate plasticizer, contaminating the packaged material; in addition, PVC material It is difficult to recycle, and incineration cannot be converted into a usable heat source. It is used as a landfill for contaminating soil and groundwater. Incineration treatment produces dioxin-causing substances, which adversely affect the human body and the environment. Therefore, the use of PVC film is worldwide. Criticism. Although cellophane itself is not toxic, its production process, like papermaking, can cause a large amount of waste waste water, which has a great impact on the environment, and the price of cellophane is also high. PET twisted film is superior to PVC twisted film and cellophane in environmental protection, but the material density is high, the price is high, and the kink performance is poor.

 The polystyrene material is odorless, non-toxic, low in price, simple in recycling process, and the used products can be recycled and recycled. It does not produce harmful substances in the process of recycling and incineration. It is a substitute for PVC twisted film, cellophane and PET twisted film. Preferred material. However, due to the difficulty in mastering the production process of polystyrene kinks, the production method of polystyrene kinks has not been reported yet. Although the polystyrene heat shrinkable film used for packaging is a well-known product, it cannot be used as a twisted film because the resilience is too large. Summary of the invention

 SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a non-resilient polystyrene twisted film, thereby realizing a non-toxic, low-cost polystyrene twisted film instead of a PVC twisted film, a cellophane or a PET twisted film as a packaging material.

 The invention includes the following steps:

A. Formulated by weight percentage of polystyrene resin, high impact polystyrene resin or modified polystyrene resin containing 60~97% melt index 0.6~5g/10min, Vicat softening point I02~108°C One or more kinds, 1~10% toughening agent, 0~30% recycled material, and then plasticized and melted in one or more extruders, extruded to form a single layer membrane or multi-layer co-extruded film The film is chilled at 45~90'C; B. The film preheated at 100~140 °C is longitudinally stretched 1:1.5~5 times, and cooled at 60~95 °C;

 C. The longitudinally stretched film is preheated at 110~140 °C, then stretched 1:3~6 times, then cooled at 70~90 °C, trimmed, and corona treated. The winding becomes a finished product.

 In the present invention, the polystyrene includes a homopolymer or a copolymer of styrene, methylstyrene, and a styrene derivative.

 High impact polystyrene is a polystyrene continuous phase and a rubber dispersed phase formed by adding one or more of butadiene rubber, styrene-butadiene rubber or nitrile rubber to polystyrene. Blend composition. Preferably, it is a blend composition of 90 to 95% by weight of general-purpose polystyrene and 5 to 10% of butadiene rubber.

 The modified polystyrene is a homopolymer or a block formed of one or more of styrene and butadiene, isoprene, acrylonitrile, maleic anhydride, methacrylate, and maleimide. Or a graft copolymer, preferably: butadiene-styrene copolymer, isoprene-styrene copolymer, acrylonitrile-styrene copolymer, methacrylate-butadiene-styrene copolymer , methacrylate-styrene copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, methyl methacrylate-acrylonitrile-butadiene-styrene copolymer, propylene Nitrile-butadiene-styrene copolymer.

，其中聚苯乙烯聚合度 500~2500， 聚顺丁二烯的聚合度为 200~1500。更优选是重量比 70〜80wt%苯乙烯和 20~30wt%丁二 烯共聚形成的共聚物。 Tougheners include styrene-cis-butadiene copolymers, styrene-isoprene copolymers, styrene-cis-butadiene-acrylonitrile copolymers, polystyrene-polybutadiene blend compositions . Preferably, 40 to 85% of styrene and 15 to 60 wt% of butadiene are copolymerized to form a copolymer having a polymerization degree of 1000 to 3000; or 60 to 80% of styrene, and 10 to 25 wt% of butadiene a copolymer of 500 to 1500 having a degree of polymerization of 10 to 20% by weight of acrylonitrile; or 40 to 85% by weight of polystyrene and

Among them, the degree of polymerization of polystyrene is 500~2500, and the degree of polymerization of polybutadiene is 200~1500. More preferably, it is a copolymer formed by copolymerization of 70 to 80% by weight of styrene and 20 to 30% by weight of butadiene.

 The polystyrene resin, the high impact polystyrene resin or the modified polystyrene resin of the present invention, and the toughening agent preferably use a transparent material in order to form a transparent film which is easily accepted. The preferred styrene resin, high impact polystyrene resin or modified polystyrene resin of the present invention has a melt index of 1.2 to 2.5 g/10 min and a Vicat softening point of 104 to 106 °C.

 The recycled material is a cleaned polystyrene (PS) pellet produced by pulverizing, filtering, and granulating the chamfer which is formed by cutting the biaxially stretched film. By adding a certain amount of recycled material, the production cost can be reduced.

In the present invention, the diaphragm is preferably composed of three or more layers, and accordingly two or more extruders are required, wherein the upper and lower surface layers can be plasticized and melted using an extruder. Can also be in the surface material Add 0.05~1% by weight of lubricant, and add 1~5% by weight of antistatic agent to the middle layer or more. The lubricant may be a commercially available lubricant for PS plastic processing, such as a C ₁₂ ~ C ₂ o higher aliphatic alcohol to lower the film friction coefficient. The antistatic agent may also be a commercially available antistatic agent for PS plastic processing, such as polyoxyethylene quaternary ammonium salt, an ionic surfactant, which improves the antistatic properties of the film.

 In the present invention, the extruder used may be a twin-screw extruder or a single-screw extruder.

 In the present invention, the preheating temperature in the longitudinal stretching and the transverse stretching is preferably 125 to 135 ° C, the longitudinal stretching ratio is preferably 1: 1.5 to 3 times, and the transverse stretching ratio is preferably 1: 4 to 5 times.

 In the step A, the chill roll temperature is preferably 65 to 75 °C. In step B, the cooling setting temperature is preferably 65 to 75 °C. In the step C, the cooling setting temperature is preferably 70 to 80 °C.

 The invention stretches and orients the polymer molecular chain in the longitudinal direction and the transverse direction in the longitudinal direction and the transverse direction to obtain better mechanical properties, high strength, high rigidity, no resilience, high tensile strength (longitudinal MD 35 MPa, Horizontal TD^50MPa), large modulus of elasticity (longitudinal MD 1800MPa, transverse TE» 1800MPa), low haze (2.9%), high gloss (45°) (121%), is a better twisted film, The film thickness is 15~50μηι, wherein the surface layer is 3~10μπι, compared with PVC twisted film, the invention is non-toxic, easy to degrade, strong in kink, good in aluminizing effect, good gloss and transparency, compared with cellophane price About 1/3 lower, it can be used as a packaging material instead of PVC twisted film, cellophane or PET twisted film. detailed description

 Example 1

 Materials used:

 High impact polystyrene: transparent, melt index 1.5g/10min, Vicat softening point 105 ° C, 92% by weight polystyrene and 8% butadiene rubber blend composition;

Toughening agent: K resin of KR-03 model of Philips, Netherlands, transparent, is a product with an average molecular weight of about 1.8xl ⁵ formed by copolymerization of 75% styrene and 25% butadiene;

 Antistatic agent: The model produced by China Shantou Divis Co., Ltd. is AMS-576;

 Lubricant: The model manufactured by Exxon Corporation of the United States is CASS112.

 The above materials are prepared as intermediate materials by weight ratio: 92% high impact polystyrene, 5% toughening agent, 3% antistatic agent; surface layer material: 94.5% high impact polystyrene, 5% toughening agent, 0.5% lubricant.

After the materials of each layer are uniformly mixed, they are separated by metal separators, and the metal chips or particles entrained in the materials are separated and sent to two twin-screw extruders for plasticizing and melting. The melting temperature is 210 ° C, and the melt is in the screw. high speed It is uniformly mixed and conveyed under rotation. During the transport process, the low molecular weight gas and the decomposed gas in the melt pass through the vent hole of the extruder and are sucked into the condensing system by the vacuum pump to separate the low molecular substances. Filtration removes poorly plasticized materials and impurities to ensure a high degree of purity. The melt is laminated in the τ-shaped die by the upper, middle and lower layers at a flow rate of 1:6:1 through the sizing surface of the lip to form a uniform film having a thickness of 450 μm and consisting of three layers. The squeezing roller with a high degree of smoothness and a temperature of 70 ° C is quenched into a diaphragm and thickness-measured. The diaphragm thickness is determined by the die adjustment.

 The film after quenching and setting is preheated by a multi-pass preheating roll at 130 ° C, and the speed difference between the slow speed roller and the fast roller is stretched once at a draw ratio of 1:2.5, and cooled by a 70 ° C cooling roll. , complete the longitudinal stretch.

 The longitudinally stretched film was preheated to 130 ° C, and the film was pulled by a chain clamp using an adjustable rail, and the transverse stretching was performed at a draw ratio of 1:4.5, and then cooled at 75 ° C for setting. In the transverse stretching process, the thickness of the film after stretching is controlled to be between 15 and 50 μm, which is unqualified by the on-line thickness gauge and treated as waste.

 The stretched film is first cut off by a trimming machine, and then subjected to high frequency corona treatment by a corona machine to increase the adhesion and friction of the printing ink. The corona-treated film is wound into a bundle on a winder, and then naturally placed for a period of time for aging treatment to stabilize the performance of the product.

 After the aging treatment, the biaxially oriented polystyrene film is cut into the specifications required by the user by a slitting machine, and then packaged to obtain a biaxially stretched polystyrene twisted film product.

 The above kink film thickness is 40 μm, wherein the thickness of the upper and lower surface layers is 5 μπι, the finished product is tested, the tensile strength is MD: 56.3 MPa, the transverse TD: 77.1 MPa, the elastic modulus is MD: 2899 MPa, the transverse TD is 3439 MPa, haze: 2.9%, gloss (45°): 121%, does not have resilience, is a better kink film. Example 2

 Materials used:

 Modified polystyrene: transparent, melt index 2.5 g/10 min, Vicat softening point 105 ° C, 70% by weight copolymer of styrene, 20% butadiene and 10% acrylonitrile;

 Recycled material: cleaned PS pellets obtained by pulverizing, melting, filtering and granulating the products after stretching to obtain the finished scraps after trimming;

 The toughening agent, antiblocking agent, antistatic agent, and lubricant were the same as in Example 1.

 The above materials are prepared according to the weight ratio of the intermediate layer material: 75% modified polystyrene, 8% toughening agent, 15% recycled material, 2% antistatic agent; surface layer material: 91.5% modified polystyrene, 8% increase Toughener, 0.5% lubricant.

The process steps are the same as in Example 1, and the stretching conditions are as follows: Cooling roll temperature after extrusion of T-die

Longitudinal stretching preheating roll temperature 135'C, draw ratio 1: 2.0, longitudinal stretch cooling set temperature 70'C _; transverse stretch preheating temperature 135 °C, draw ratio 1: 4.5, transverse stretch cooling set Temperature 75 ° C.

 The thickness of the kink film obtained is 28 μm, wherein the thickness of the upper and lower surface layers is 5 μη, the finished product is tested, and the tensile strength is longitudinal MD: 52.8 MPa, transverse TD: 75.2 MPa, elastic modulus longitudinal MD: 2853 MPa, transverse TD:

3408MPa, haze: 2.8%, gloss (45°): 122.5%, does not have resilience, is a better kink film. Example 3

 Materials used - high impact polystyrene: transparent, melt index 2.5 g/10 min, Vicat softening point 105 ° C, 90% by weight copolymer of styrene and 10% cis-butadiene, degree of polymerization 1500.

 The regrind, the toughening agent, the antiblocking agent, the antistatic agent, and the lubricant were the same as in Example 2.

 The above materials were formulated as intermediate materials by weight ratio: 75.5% high impact polystyrene, 8% toughening agent, 10% recycled material, 4% antistatic agent, 0.5% lubricant.

 The single-layer film was formed by plasticating and melt-extruding from a twin-screw extruder. The other process steps were the same as in Example 1, and the stretching conditions were as follows:

The cooling roll temperature after extrusion of the T-die is 70 ° C _;

 Longitudinal stretching preheating roll temperature 135'C, draw ratio 1: 2.0, longitudinal stretch cooling set temperature 70'C; transverse stretch preheating temperature 135'C, draw ratio 1: 4.5, transverse stretch cooling set Temperature 75 ° C.

 The obtained kink film thickness is 30μπι, the finished product is tested, tensile strength MD: 53.5MPa, transverse TD: 74.3MPa, elastic modulus MD: 2898MPa, transverse TD: 3512MPa, haze: 2.9%, gloss (45 °): 122%, does not have resilience, is a better kink film. Example 4

 Materials used:

 Polystyrene: transparent, melt index 2g/10min, Vicat softening point 105 °C.

 The regrind, the toughening agent, the antiblocking agent, the antistatic agent, and the lubricant were the same as in Example 2.

The above materials are formulated in an intermediate layer material by weight ratio: 75% high impact polystyrene, 10% toughening agent, 10% recycled material, 5% antistatic agent. Surface layer material: 89.5% of the high impact polystyrene described in Example 1, 10% toughening agent, 0.5% lubricant.

 The process steps are the same as in Example 1, and the stretching conditions are as follows:

 The chill roll after extrusion of the T-die is 70 ° C;

 Longitudinal stretching preheating roll temperature 135 ° C, draw ratio 1: 2.0, longitudinal stretch cooling set temperature 70'C; transverse stretch preheating temperature 135 ° C, draw ratio 1: 4.5, transverse stretch cooling set Temperature 75 ° C.

 The obtained twisted film thickness is 20 μm, wherein the thickness of the upper and lower surface layers is 3 μm, and the finished product is tested, tensile strength, longitudinal MD: 52 MPa, transverse TD: 77.8 MPa, elastic modulus, longitudinal MD: 2931 MPa, transverse TO: 3388 MPa, haze : 2.7%, gloss (45°): 123%, does not have resilience, is a better kink film.

Claims

Rights request A method of producing a polystyrene twisted film, comprising the steps of:  A. Formulated by weight percentage of polystyrene resin, high impact polystyrene resin or modified polystyrene resin containing 60~97% melt index 0.6~5g/10min, Vicat softening point 102~108'C One or more kinds, 1~10% toughening agent, 0~30% recycled material, and then plasticized and melted in one or more extruders, extruded to form a single layer membrane or multi-layer co-extruded film Film, the film is quenched and set at 45~90 °C;  B. The film preheated at 100~140 °C is longitudinally stretched 1: 1.5~5 times, 'cooling at 60~95'C;  C. The longitudinally stretched film is preheated at 110~140 °C, then stretched 1:3~6 times, then cooled at 70~90'C, trimmed, and corona treated. Winding up into a finished product;  The toughening agent is one or more selected from the group consisting of styrene-cis-butadiene copolymer, styrene-isoprene copolymer, styrene-cis-butadiene-acrylonitrile copolymer, a polystyrene-polybutadiene blend composition; the recycled material is a clean polystyrene pellet produced by pulverizing, filtering, and granulating the chamfer which is formed by cutting the biaxially stretched film.  2. The method according to claim 1, wherein the polystyrene resin, the high impact polystyrene resin or the modified polystyrene resin has a melt index of 1.2 to 2.5 g/10 min, and a Vicat softening point. It is 104~106 °C.  The method according to claim 1, wherein the polystyrene resin, the high impact polystyrene resin or the modified polystyrene resin is a transparent material.  The method according to claim 1, wherein the toughening agent is a polymerization degree of 1000 to 85% by weight of styrene and 15 to 60% of cis-butadiene or isoprene. ~3000 copolymer; or 60~80% styrene, 10~25% cis-butadiene and 10-20% acrylonitrile copolymerized with a copolymerization degree of 500-1500 copolymer.  5. The method according to claim 1, wherein the toughening agent is a blend composition of 40-85% by weight of polystyrene and 15~60% of polycis butadiene, wherein the toughening agent is polystyrene. The polymerization degree is 500~2500, and the polymerization degree of polybutadiene is 200~1500.  The method according to claim 4, wherein the toughening agent is a copolymer formed by copolymerization of 70 to 80% by weight of styrene and 20 to 30% of butadiene. 7. The method according to claim 1, wherein the diaphragm is composed of three or more layers, and The material in the two surface layers also contains 0.05 to 1% by weight of the lubricant, and the middle layer or more also contains 1 to 5% by weight of the antistatic agent.  The method according to claim 1, characterized in that the method satisfies one or both of the following conditions: the longitudinal stretching ratio of the film is 1: 1.5 to 3 times, and the transverse stretching ratio is 1: 4~ 5 times.  9. The method according to claim 1, wherein the longitudinal stretching and/or the transverse stretching preheating temperature is 125 to 135 °C.  10. The method according to claim 1, wherein the method satisfies one or more of the following conditions: a cooling roll temperature of step A is 65 to 75 'C, and a cooling setting temperature of step B is 65 to 75 ° C. The cooling setting temperature of step C is 70 to 80 °C.