JPS60157824A - Preparation of improved agricultural film - Google Patents

Abstract

PURPOSE:To prevent foams from mixing into film product by providing a hygroscopic resin compound layer supplied by a specified vent type extruder. CONSTITUTION:Hygroscopic resin compound is supplied from a vent type extruder 1 capable of peculiarly controlling a feed quantity Q1 from a hopper section to a vent section and a feed quantity Q2 from the vent section down to a die discharge section. This resin compound and the resin supplied by an extruder 2 are discharged through a multilayer blown film die 3. It is possible to prevent foams from mixing into film by hygroscopicity and to obtain polyolefin multilayer film containing hygroscopic resin compound as a constituent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyolefin agricultural film having a multilayer structure in which at least one layer is provided with a hygroscopic resin composition layer in multilayer inflation processing or multilayer T-die processing.

In recent years, composite films in which various additives are mixed into each layer of a multilayer structure have been widely used in order to impart many functionalities to polyolefin agricultural films. In film processing where one composition is a hygroscopic resin composition containing a filler, the water released during processing evaporates and vaporizes, creating air bubbles in the product. This will save you a lot of effort.

For this reason, it is generally considered that a vent section is provided in the extrusion mode for supplying and discharging the hygroscopic resin composition to remove moisture during processing, but film processing dies tend to have high resistance in the flow path in order to improve thickness accuracy. In addition, multilayer dies have complex and long flow paths, and the pressure at the extruder head reaches 25 okq/d or more under normal processing conditions. Thereafter, the amount of resin fed to the extruder is greatly affected by the back pressure flow, and the apparent volume expansion during foaming at the vent section due to differences in the bulk density, melted density, and water content of the hygroscopic resin composition pellets, and processing. Due to the difference in melt viscosity etc. due to temperature, the feed amount Q from the pothole part to the vent part with a bent type single screw,
(hereinafter abbreviated as Q1) and feed jtQ2 (hereinafter abbreviated as Q2) from the vent part to the die discharge part match at a certain point and perform stable processing, no matter how much screw design technology is used, it is extremely difficult. .

If 0.1 <Q2, the area after the vent becomes starved and a surging phenomenon occurs, which seriously affects the unevenness of the film thickness.

On the other hand, if Ql > Q2, the molten resin equivalent to Q and -Q2 will overflow from the vent hole, and the vent effect will not be achieved completely, resulting in problems such as bubbles in the film product. becomes.

As a result of intensive studies to solve these problems, the present inventors have developed an adjustment structure that can independently adjust Ql and Q2 in order to prevent air bubbles from being mixed into film products due to hygroscopic moisture and to stably process films. The present invention was achieved by discovering a method for producing a polyolefin agricultural multilayer film using an apparatus having a vent-type extruder.

The polyolefin resin used in the present invention is a homopolymer of α-olefin, or a copolymer with a different monomer mainly composed of α-olefin, such as polyethylene, polypropylene, ethylene-propylene copolymer, Ethylene-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, Ethylene-
Examples include methyl (meth)ac IJ L/-74 combination, ethylene-ethyl acrylate copolymer, and ionomer resin. Examples of highly hygroscopic water-containing fillers used in the present invention include silica gel, silica aluminum silicate gel, aluminosilicate gel, titanium silicate gel, calcium silicate gel, magnesium silicate gel, zeolite, talc, bolast, kaolinite, mica, calcium carbonate, etc. Examples include synthetic or natural inorganic fillers, and synthetic or natural organic fillers such as polyvinyl alcohol, cellulose, and wood flour.

Furthermore, the hygroscopic resin composition as used in the present invention is a composition that contains water at a water content higher than that which causes processing troubles such as foaming in substantially normal non-vent processing, and more specifically, at 110°C. This is a composition containing water whose loss on heating is 0.2% by weight or more. Furthermore, various additives such as a droplet-free agent, a stabilizer, an ultraviolet absorber, an anti-blocking agent, a lubricant, and a coloring agent can be appropriately mixed into each resin layer as required.

Conventional vented extruders adjust Ql and Q2 using a single screw, so even though Q2 changes greatly due to fluctuations in tip head pressure, Ql is not directly affected by tip head pressure and is Since the feed amount is uniquely constant depending on the rotation speed, Q2 is maintained before and after the vent part.
It tends to be difficult to balance Ql commensurate with Stable machining was extremely difficult. In extreme cases, in order to achieve Qr''' Qt in a single vented screw, the flow characteristics of the composition, head pressure, processing source conditions, water content of the composition, processing density of the composition pellets, melting time Elements including density, etc., are only available under - conditions, and a slight variation in any of the elements will impede stable processing.

The feature of the present invention is that it is equipped with a device having an adjustment structure that can independently adjust Ql and Qt in order to solve these problems at once and create a structure with excellent stable workability. A normal extruder (hereinafter referred to as the first extruder) that is in charge of Ql, and a separate extruder that has a vent structure and is in charge of Qt that feeds the resin composition melt-fed from the first extruder to the die part. (hereinafter referred to as the second extruder), Qt and Ql are controlled at their own screw rotation speeds according to the desired Qt.
By adjusting so that r = Q2 and by incorporating a gear pump with its own drive between the single-screw vent type extruder and the die, the pressure loss in the die part is directly received by the gear pump and transferred to the die part. There is a method that not only ensures the quantitative quality of be. In the former method, Qr and Qt are each fed by two separate extruders, so it is possible to make the equipment more compact. Not only is it easy to use a rotating and sliding system that integrates the two, but it is also possible to further downsize and save energy by incorporating a solid forced-feed type extruder into the first extruder.

On the other hand, the latter uses the pressure increase before and after the gear pump and the quantitative feed effect to lower the resin pressure at the screw tip (gear pump inlet side), making it possible to reduce the influence of back pressure flow on the Q2 side and venting. Thereafter, the length L/D of the cylinder up to the tip of the screw can be reduced, making it possible to make the entire structure more compact and save energy.

Next, an example of the present invention will be explained with reference to the drawings.

1.2 are explanatory diagrams each showing an apparatus for carrying out the present invention.

In the first cell, 1 is a two-stage vent extruder that melts and extrudes absorbed water from a hygroscopic resin composition containing a hygroscopic filler while dehumidifying it in a vent section, and is supplied from a separate extruder 2. The resin that does not contain hygroscopic filler is
The resin fed from the vented extruder 1 is laminated with the resin supplied from the vented extruder 1 in the multilayer inflation die 8, and the resin discharged from the lip is cooled while blowing up to form a hygroscopic resin composition with a multiphase structure as one component. This makes it possible to produce a polyolefin agricultural film in which no air bubbles are observed within the film due to moisture absorption, despite the presence of moisture.

The hygroscopic resin composition pellets supplied from the hopper 6 of the first extruder 4 are melt-kneaded by the screw 7, reach the tip of the extruder, and then pass through the connecting pipe 8 to the second extruder 9.
It is directly fed in a molten state to the feed section of the This second extruder screw is rotated by a drive source different from the first extruder screw, and while the molten resin is being extruded by the screw 11, the vent part 1 directly connected to the vacuum pump 18
2, the moisture that has been absorbed is completely removed by suctioning under reduced pressure while transpiring and vaporizing it, and then the flange that directly connects the die 3 and the cylinder is fed to the tip of the screw while being recompressed. A fixed amount is supplied to the dice through 14.

Feed amount Q2 to the vent section and unloading die section as desired
is determined by the screw rotation speed of the second extruder driven by the motor IO. By constantly controlling the process, it is possible to obtain a stable agricultural multilayer film even though it is bent.

In FIG. 2, reference numeral 21 denotes a device in which a gear pump 28 is installed at the tip of a single-screw vent extruder 22 that melts and extrudes moisture absorbed by a hygroscopic resin composition containing a hygroscopic filler while dehumidifying it in a vent section. , a separate extruder 2
The resin containing no hygroscopic filler supplied from step 4 is laminated with the resin supplied from the vent extrusion device 24 in the multilayer inflation die 25. By cooling the resin discharged from the pump while blowing it up, a hygroscopic resin composition with a multi-M structure is produced. This makes it possible to produce films for

The hygroscopic resin composition pellets supplied from the hopper 27 of the vented extruder 22 are melted and kneaded by the screw 28, and are then melted and kneaded under reduced pressure in the vent section 2 directly connected to the vacuum pump 80 while transpiring and vaporizing the absorbed moisture. After the water is completely removed by suction, it is fed to the tip of the screenie while being recompressed, and directly fed in a fixed amount to the die part 25 in a molten state by the gear pump 28 built in between the tip of the extruder and the die. .

Feed ff1Q2 to the die section as desired is determined by the rotation speed of the gear pump driven by the motor 81, and the screw of the vent type extruder 22 is adjusted while monitoring the decrease in venting effect due to surging of Q2 and venting up at the vent section. By constantly controlling the rotation speed by the motor 26, it is possible to obtain a stable agricultural multilayer film with vent processing.

As described above, the device shown in FIGS. 1 and 2 is a multilayer inflation device with 8 layers of 2 types, but it is within the scope of the present invention to manufacture the device with a more complicated structure such as 8 layers of 3 types, etc., if necessary. Of course, the present invention is the first apparatus to have a multilayer film processing die with high die head pressure, and is capable of producing films using a hygroscopic resin composition as a component, while also being able to produce films using a stable vent processing method. , an extremely useful agricultural film that completely prevents air bubbles from being mixed into the film due to moisture absorption, and has made it possible to provide a high-performance polyolefin agricultural multi-shine film that has a wide range of functions including heat retention. It is a film processing technology.

[Brief explanation of the drawing]

FIG. 1 schematically shows an example of the method for manufacturing an agricultural multilayer film having a two-stage vent extrusion structure according to the present invention, and the names of the parts indicated at the middle of the figure are shown below. 1. Entire 2 general vent extruder 2. Extruder 8. Multilayer inflation die C2M 18 layers) 4.
1st stage extruder main body 56 for venting 1st stage extruder drive motor 6 for venting, hopper 7, screw 8 for 1st stage extruder venting, connecting pipe 9, 2nd stage extruder main body 10 for venting, venting 2nd stage extruder drive motor 11, vent 2nd stage extruder screw roller 12, vent gage 18, vacuum pump 14, flange Figure 2 shows the assembly structure of the single shaft vent type extruder and gear pump according to the present invention. This diagram schematically shows an example of a method for manufacturing an agricultural multilayer film having the following, and the names of the parts shown in the figure are shown below. 21, entire structure incorporating a single-screw vent type extruder and a gear pump 22, a single-screw vent type extruder main body 28, a gear pump main body 24, an extruder 25, a multilayer inflation die (2 fine 8 layers) 26,
Drive motor 27 for single-screw vented extruder, hopper 28, screw 29 for single-screw vented extruder, vent β 80. Vacuum pump 81, gear pump drive motor 323 flange

Claims (1)

[Claims] (1) In multilayer inflation processing or multilayer T-die processing, at least one layer can adjust the feed amount Q1 from a part of the hopper to the vent section and the feed amount Q2 from the vent section to the die discharge section. A method for producing a polyolefin agricultural film having a multilayer structure comprising layers of a hygroscopic resin composition supplied by a vent-type extruder having a flow rate adjustment mechanism. (2) It consists of a first extruder that is in charge from a part of the hopper to a vent part, and a separate extruder that has a vent structure and feeds the resin composition melt-fed from the first extruder to a die part, and a part of the hopper. Feed f to the vent part
lQt and feed NQ from the vent to the die discharge part,
Ql by controlling each unique screw rotation speed.
, Q. A method for producing an agricultural film, comprising using a vent-type extruder having a structure for adjusting . (8) A gear pump with its own drive is installed between the single-screw vent type extruder and the die, and by controlling the rotation speed of the screw and gear pump of the vent extruder, the feed amount Q1 from the hopper part to the vent part can be adjusted. A method for producing a vented and later diced olefin-based agricultural film.