JPH01218815A - Manufacture of low-density foamed polystyrene - Google Patents

Abstract

PURPOSE: To obtain a product having a buoyancy, a cold resistance and a moisture resistance by mixing a low density polyethylene, a foaming agent and a surfactant, and processing it at a series of different temperatures. CONSTITUTION: A mixture is prepared by mixing a low density polyethylene with an azodicarvone amide as a foaming agent, a zinc oxide as a surfactant, a ZnC as a release agent and a fluorocarbon as a gas foaming agent. The mixture is melted at 170 deg.C at a first stage of a heating tunnel. A melted lump is moved to a second stage held at 200 deg.C. Then, when the lump is cooled to 150 deg.C at a third stage, foam is cured and contracted. A fluorocarbon is introduced, the lump is foamed, lowered to 100 deg.C to a state adapted to cutting. The lump is extruded into an atmosphere at about 25 deg.C, and a sheet having a thickness of about 1 mm is formed via rollers. It is then left to stand for 24 hours at 25 deg.C. Thin garments having a light weight can be provided with the polyethylene product.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a low-density foamed polyethylene sheet or tube having buoyancy, cold resistance and moisture resistance, a method for producing this type of low-density foamed polyethylene, and Concerning clothing and devices that require both sexes.

[Prior art and the problem that the invention seeks to solve] Clothing with buoyancy, cold resistance, and waterproofness is highly desirable in many situations, and uniforms and jackets with all of these properties are highly desirable. Equipped outdoorsmen have an advantage in a variety of situations.

For example, the ability to move under adverse conditions on uneven terrain is
It would be greatly enhanced by clothing that is cold-resistant and protects from the outside air when worn, and at the same time is buoyant and waterproof, making it easy to cross or ford rivers. Climbers and hikers would similarly find benefits in this type of clothing where there is always the possibility of having to cross rivers, deal with floods, or endure cold temperatures. To get the most out of this type of clothing, it is necessary that it not only have a variety of properties, but also be comfortable and not bulky or cumbersome.

Enthusiasts of water sports should also find particular advantages in this type of clothing. Clothing that is buoyant, cold resistant and waterproof is indeed ideal for many activities and should find many uses.

The use of foam materials in various garments to provide insulation is known. U.S. Pat. No. 2,976,539 discloses an insulating garment using a closed cell foamed cellular material, preferably polyvinyl chloride, as the lining. This clothing is bulky, cumbersome, and does not have sufficient buoyancy to support your weight in the water. Similarly, U.S. Patent No. 351
No. 1743 discloses insulating laminates for space suits and diving suits in which the core is an open or closed cell sponge or foam. A fluid-impermeable rubber or plastic skin is required. This laminate exhibits moderate mobility, but is still fairly cumbersome and insufficiently buoyant for use as lifesaving equipment.

Polyethylene foam has been proposed as insulation or filling material for liferafts and life jackets. U.S. Pat. No. 3,067,147 discloses a low density polyethylene foam for this purpose treated with the blowing agent 1,2-dichlorotetrafluoroethene.

The polyethylene and blowing agent are heated under pressure and explosively extruded into the atmosphere to form a foamed cellular ring. The product is bulky and difficult to handle in actual use. Similarly, U.S. Pat. No. 3,819,543 discloses shaped chlorinated crosslinked polyethylene foams for use in making floats and garment linings. The use of various known blowing agents and crosslinking agents is suggested in this document. The molded product is thick and difficult to handle.

Despite these advancements, it has achieved excellent buoyancy, cold resistance, and water resistance without compromising mobility when worn.
There is a need for thin, lightweight materials for use as liners for clothing and outdoor equipment.

It is an object of the present invention to obviate the above-mentioned drawbacks by providing a foamed expanded low density polyethylene having both excellent buoyancy and heat resistance.

Another object of the present invention is to provide a method for producing expanded low-density polyethylene having both excellent buoyancy and heat resistance.

Yet another object of the present invention is to create a thin and lightweight product for use in clothing and sports, business, military and other related equipment, having both good buoyancy and heat resistance, while not being unwieldy or bulky. lining.

[Means to solve problems]

These and other objectives are achieved by the present invention. The present invention involves mixing low-density polyethylene with a blowing agent, a surfactant, and preferably a release agent, heating the resulting mixture to form a softened mass, and increasing the temperature of the softening ring to form bubbles in the polyethylene. The blowing agent is vaporized to foam and expand the foam, the temperature of the expanded polyethylene is lowered to partially deflate and harden the polyethylene cells, and the gaseous blowing agent is introduced into the polyethylene mass to further expand the polyethylene cells. foam and expand, cool the mass to a suitable temperature for cutting, cut and heat the mass to a suitable temperature for extrusion, extrude the mass, cool the mass into a sheet or tube for at least 24 hours at room temperature for excellent buoyancy and forming a low density polyethylene sheet or tube characterized by heat resistance.

The invention further provides expanded low density polyethylene sheets or tubes made by the method of the invention.

The present invention further provides a garment using an expanded low density polyethylene lining having a thickness ranging from about 0.5 mm to about 1 mm, and in which a lining of about 300 g can sustain a weight of about 130 kg or more. provide products.

In one preferred embodiment of the method of the invention, azodicarbonamide is a blowing agent, zinc oxide is a surfactant, ZnC is a release agent, Freon is a gas blowing agent, and the expanded low density polyethylene sheet is buoyant, water repellent and heat resistant. Formed for use as a liner for clothing that requires compatibility.

The invention will be better understood from the following detailed description of the preferred embodiments.

[Detailed description of the invention]

In the present invention, conventionally produced low density polyethylene is mixed, for example in a hopper, with a first blowing agent, a surfactant, and preferably a release agent to form a dry mixture. The dry mixture is conveyed to a closed heating tunnel where it is processed in a series of different temperature stages.

A conventional thermocouple control box can be used to maintain the specific temperature required at each processing step in the heating tunnel.

The mixture is conveyed through the first part of the heating tunnel by a conventional coil or screw.

Pressurized air is supplied from a pressurized box at the entrance end of the heating tunnel to assist in transporting the mixture through the heating tunnel.

In the first stage of the heating tunnel, the mixture is heated e.g.
Heating to a temperature of 0"C melts and forms a softened polyethylene mass. In the second stage of the heating tunnel, the molten mass is vaporized according to the vaporization temperature of the blowing agent, and the mass is further melted. The blowing agent and air begin to penetrate the cells of the molten low-density polyethylene mass, and cell expansion occurs. Some blowing agents vaporize to release nitrogen and react to release carbon dioxide. The carbon monoxide that forms is released. This carbon dioxide then penetrates the cells of the low density polyethylene, causing foaming and expansion of the cells, ie, foaming.

In the third stage of the heating tunnel, the expanded polyethylene is treated at a temperature of, for example, about 150° C. to partially deflate and harden the expanded cells of the polyethylene mass.

Low density polyethylene (LDPE) is well known in the art and has a density ranging from about 10 to about 40 pounds per cubic foot;
Considering that the density of water is 1, it is about 0.
Characterized by a density ratio of 910 to about 0.925. This makes high density polyethylene unsuitable for use in the present invention.

Suitable blowing agents to be initially mixed with the low density polyethylene, preferably in powder form, include azodicarbonamide (
Celogen AZKemp
commercially available as ore). (vaporization temperature approximately 195℃), N,
N'-Dinitrosometamethylene-tetramine (Commercially available as Unicel NDX. Vaporization temperature approx.
95°C), and 4.4°-Oxybis(Celogen OT
It is commercially available as (vaporization temperature: approximately 150°C). The amount of blowing agent added is essentially about 1% by weight of the polyethylene. Amounts of blowing agent substantially greater than about 1% cause the polyethylene cells to expand too much and are not useful for purposes of this invention.

Similarly, amounts of blowing agent substantially less than 1% do not result in sufficient cell expansion for purposes of the present invention.

Azodicarbonamide is a preferred starting blowing agent, especially when making linings for clothing, bedding and other articles for immediate wear or use. Azodicarbonamide is odorless, non-toxic, does not cause discoloration of the final product, and produces the highest amount of gas for foaming. By comparison, for azodicarbonamide per gram of solids approximately 2
20 cc of gas are produced, whereas 4.4'-oxybis produces 130 cc/g and N,N'-dinitrosopentamethylene-tetramine produces 210 cc/g.

Suitable surfactants for initial admixture with the low density polyethylene, preferably in powder form, include zinc oxide, cadmium oxide, and calcium carbide. The surfactant is
An amount ranging from about 0.1 to about 0.2% by weight of polyethylene is added.

Surfactants serve several important functions.

Firstly, the surfactant keeps the temperature of the heating tunnel low during the foaming process, while preventing the expansion of the LDPE cells from becoming too rapid during foaming. For example, when azodicarbonamide is used as the blowing agent, the surfactant helps maintain the temperature in the third stage of the heating tunnel at around 150°C. When no surfactant is used, the temperature rises to about 196° C. due to the vaporized foaming agent, resulting in unexpected excessive foaming in the present invention.

It is preferred, but not necessary, to add a release agent during the initial mixing step. A suitable release agent to initially mix with the low density polyethylene is ZnC. The release agent, preferably added in powder form, helps prevent the LDPE from sticking to the coils or walls of the heating tunnel.

The amount of release agent added is essentially about 0.3% by weight of the polyethylene.

In the fourth stage of the heat tunnel, a gaseous blowing agent is introduced into the polyethylene mass to subject the polyethylene mass to a second stage of cell expansion and to strengthen the foamed cells of the polyethylene mass. This second blowing agent is introduced at a pressure of approximately 35 kg/cm''.

A preferred gaseous blowing agent is Freon, the well-known trademark for dichlorofluoromethane, but liquefied petroleum gas (LPG) or a mixture of Freon and liquefied petroleum gas may also be used. Other suitable gas blowing agents include monochlorodifluoromethane and dichlorodifluoroethane. L
Although the advantage of using PG is that it is inexpensive, LPG has inherently toxic effects. Therefore, when producing foamed polyethylene for lining clothing, bedding, etc., it is preferable to use a foaming agent that does not inherently have toxic effects.

After introducing the gas blowing agent and further expanding the polyethylene mass, the polyethylene mass is heated to about 1
At this stage, the polyethylene mass begins to cool.

Processing at about 100°C produces a polyethylene mass suitable for proper and efficient cutting. This completes the heating and foaming process.

Stages one through five in the heating tunnel take about 30 minutes to about 1 hour to complete, with each stage taking approximately the same amount of time.

The expanded mass continues to move through the second part of the heating tunnel, which has no coils or screws inside.

In this second part of the heating tunnel, the expanded mass is cut as desired, for example by means of a conventional blade. The expanded mass is still in a softened state. The desired amount will, of course, depend on the desired final sheet or tube dimensions.

The cut expanded mass is then brought to a temperature of about 105° C. in a heating tunnel and extruded through gouers and mandrels at atmospheric pressure into a free expansion and cooling zone at room temperature. A temperature of about 100° C. is too low for proper extrusion, so it is necessary to slightly increase the temperature of the polyester mass after cutting. After extrusion, the foamed polyethylene mass expands naturally in the atmosphere, but not explosively, and cools at room temperature for a short period of time, for example 2-3 seconds. The cooling polyethylene mass is then conventionally formed into sheets or tubes, the thickness or diameter of which is determined by the intended end use of the product.

The sheet or tube is then rolled onto a roll and then at room temperature (20°C to 30°C, preferably 25°C).
Refrigerate for at least 24 hours. The sheet or tube undergoes two stages during this 24 hour cooling period. First, the bubbles of the expanded mass collapse as the blowing agent and air trapped in the bubbles escape from the bubbles. Over the next 24 hours, air re-penetrates the bubbles, causing them to expand to an intermediate stage.

The final product is a low-density polyethylene consisting of a tightly packed network of numerous small air-filled cells. The weight of the final product corresponds to the weight of the initial low density polyethylene. Thus, for example, 25 kg of low density polyethylene yields 25 kg of finished sheet.

Accordingly, the present invention provides two CH2-CI sheets having a weight ranging from about 12 g/sq yd to about 21 g/sq yd for sheets having a thickness ranging from about 0.5 to about 1 mm.
A foam expanded low-density sheet or tube of polyethylene (2) is obtained. This sheet is characterized by excellent buoyancy and heat resistance. For example, 300 g of finished product can float a weight of more than 130 kg. The density ratio of the product will range from about 0.4 to about 0.55 compared to water, considering that water has a density of 1.

Additionally, sheets or tubes of low density expanded polyethylene are cold resistant, water clear and moisture resistant.

The expanded foamed low-density polyethylene of the present invention can be formed into a sheet having any thickness, but from about 0.5 mm to
Preferably, the thickness is in the range of about 5M. For clothing, the thickness of the sheet should be about 0.5 mm or more and about 11 mm or less. Sheets with a thickness significantly less than 0.5 nwn have insufficient buoyancy for practical use in the present invention. On the other hand, a sheet having a thickness significantly greater than about 111111 is unsuitable for use in the clothing of the present invention because it results in clothing that is uncomfortable to wear. When the low density polyethylene sheets of the present invention are intended to be used as liners for tents, bedding, blankets and similar equipment,
Thicknesses of about 5 rm or less are advantageous because they can be used without making the equipment unnecessarily bulky and unwieldy.

Customary additives such as fire retardants or flame retardants, such as tin, can also be added in appropriate amounts during the mixing step to impart further properties to the final product. These conventional additives slightly increase the weight of the final product, but do not significantly affect the buoyancy or thermal properties of the final product. Examples of additives include about 0.0% of polyethylene, which can be added in powder form to increase the tear resistance of the final product.
There is 1 to about 0.2% by weight of a crosslinking agent, such as azobisformamide (ABFA) or dicumyl peroxide, and about 0.1% of a UV absorber to prevent discoloration. After the expanded polyethylene is formed into a sheet, or simultaneously with the sheet forming process, the polyethylene can be sandwiched between the sheets on both sides, and the materials on both sides can be nylon, vinyl, plastic, gauze, thin cloth, or It can be a coating of any material.

The polyethylene is still somewhat softened at this point, so the material on both sides adheres slightly to the polyethylene. More importantly, pinching from both sides at this point facilitates the process of sewing the material sheathing on both sides to the polyethylene, as well as the process of cutting and transporting the final product.

Such material coating also increases the durability of the sheet.

The low molecular weight foamed polyethylene produced according to the present invention is
Since this product is water-repellent and moisture-resistant, its storage does not require special conditions even during the last 24-hour cooling period.

Also, in the method of the present invention, no polyethylene is wasted.

For example, from 10 g of low density polyethylene starting material,
10 g of expanded foamed low density polyethylene produced according to the invention is obtained.

The diameter of the polyethylene tubes produced according to the present invention will vary depending on the end use. Extruded tubes can be solid or hollow and find particular use as buoyancy materials around ships.

〔Example〕

25 kg of low density polyethylene in a hopper
of azodicarbonamide, 40 g of zinc oxide, and 7
Mix with 5g of ZnC.

This mixture is fed into a heating tunnel equipped with a screw that provides the mixture through the tunnel.

Air supplied from the pressurized box helps transport the mixture.''The mixture is heated to 170°C in the first stage of the tunnel, at which point the mixture melts.The molten mass is kept at a temperature of 200°C. The mass is then transferred to the second stage of the tunnel, where the azodicarbonamide vaporizes and penetrates, expanding the polyethylene bubbles.The mass is then brought to a temperature of 150°C in the third stage, and as the mass is cooled, the bubbles form. hardens and shrinks slightly. Freon is then introduced at 35 kg/cm'' to further expand and foam the mass. Next, set the temperature of the mass to 100'C.
to make the mass suitable for cutting.

Cut the mass with a blade so that it separates from subsequent batches of the tunnel. Prepare the mass for extrusion by increasing the temperature of the mass to 105°C. The mass is extruded into ambient air at room temperature of 25°C. Expansion occurs but the mass does not explode. The extruded mass is 2~
Cool in 3 seconds, then pass through a roller and form into a 1 inch thick sheet. Form the continuous sheet into 4 rolls, 2
Store at 5°C for 24 hours. The final product has a thickness of IIWl
The length is 300m, the weight is 21g/square yard, and the thermal transmittance is 300m.
ance) is 6.70w/m”C, thermal transmittance (the
rmal transmission) is 52.5% (
AsTMD 151B), water absorption is 9. lX10-
lb/ft (B 33595-1969) Tyrol expanded polyethylene. A completed 300g sheet can hold more than 300kg of weight floating.

As mentioned above, the expanded low-density polyethylene of the present invention can be used for clothing,
Bedding, blankets, cushions, sports and leisure equipment such as tents, bags, bags, rafts,
It has a wide variety of uses as a lining for deck chairs and related items.

〔Effect of the invention〕

As explained in detail above, the low density polyethylene product of the present invention combines excellent buoyancy and heat resistance, thereby eliminating the need for additional rescuers on the water. A single garment using the lining of the present invention serves as both a thermal jacket against the outside air and a general flotation and emergency flotation equipment. Furthermore, the present invention provides a lightweight and thin garment for the above-mentioned purpose, which is comfortable to wear and not cumbersome, thus improving not only safety but also comfort.

The present invention provides linings and garments that retain buoyancy and flotation even when torn or torn. Blankets and bedding can also be given buoyancy and used as flotation equipment. For example, the bulky life vests used in water skiing can be replaced with thinner, lighter life vests, improving safety and mobility in leisure sports.

Conventional clothing and related equipment for outdoor activities such as hunting, fishing, camping, etc. can be dramatically improved by the present invention, such as wearing one piece for insulation purposes,
This makes it possible to use it in emergency surfacing situations, from accidentally falling into a river to crossing a river.

Furthermore, the polyethylene products of the invention can also be used as thermal insulation, for example in radio equipment.

Although the invention has been described by reference to certain preferred embodiments, the invention is not limited to these embodiments, and those skilled in the art will appreciate that the invention can vary within the scope of the invention as set forth in the claims. I'm sure you'll be thinking of changing that.

Claims (1)

[Claims] 1. 1) mixing low-density polyethylene, a blowing agent, and a surfactant; 2) treating the resulting mixture in a closed container for about 30 minutes to about 1 hour; The resulting mixture was heated to a first temperature sufficient to melt and soften the low density polyethylene, and the softened mixture was heated to a second temperature sufficient to vaporize the blowing agent, thereby vaporizing it. 3) infiltrating the cells of the low density polyethylene with a blowing agent to foam and expand the cells of the polyethylene, and cooling the expanded and expanded polyethylene at a third temperature to partially shrink and harden the cells; cutting the partially cooled polyethylene into the desired amount; 4) extruding the cut polyethylene; 5) briefly cooling the extruded polyethylene at ambient temperature; 6) forming the polyethylene into a sheet or tube; and 7) buoyancy, cold resistance, comprising cooling the formed sheet or tube for at least 24 hours at a room temperature of about 20°C to about 30°C to first deflate the polyethylene cells and then cause the cells to return to their expanded state. and a method for producing a water-repellent low-density polyethylene sheet or tube. 2. The method of claim 1, comprising the steps of: introducing a gaseous blowing agent into the closed container after cooling the polyethylene to a third temperature to further expand and strengthen the polyethylene cells prior to cutting. . 3. The method of claim 1, wherein the blowing agent is selected from the group consisting of azocarbonamide, N,N'-dinitrosopentamethylene-tetramine, and 4,4'-oxypis. 4. The method according to claim 1, wherein the surfactant is selected from the group consisting of zinc oxide, cadmium oxide, and calcium carbide. 5. The method according to claim 2, wherein the gas blowing agent is selected from the group consisting of dichlorofluoromethane and monochlorodifluoromethane. 6. The method of claim 5, wherein the gas blowing agent is introduced at a pressure of about 35 kg/cm^2. 7. The method of claim 1, wherein a release agent is introduced in said mixing step to prevent adhesion of molten polyethylene to the surface of said closed container. 8. The method according to claim 7, wherein the release agent is ZnC and the amount of release agent introduced is about 0.3% by weight of the polyethylene. 9. The method according to claim 1, wherein the blowing agent is azodicarbonamide and the surfactant is zinc oxide. 10. The extruded polyethylene has a thickness of approximately 0 after cooling.
．． 2. The method of claim 1, wherein the sheet is in the range of 5 m to about 1 mm. 11. The extruded polyethylene has a thickness of about 5 mm after cooling.
The method according to claim 1, wherein the method is formed into a sheet having a size of 1 mm or less. 12. The method of claim 10 further comprising the step of sandwiching the formed sheet between layers of material on either side before final cooling to facilitate handling and processing of the formed sheet. the method of. 13. The method according to claim 1, wherein the room temperature during the 24-hour cooling is about 25°C. 14. The method of claim 1, wherein the amount of blowing agent is about 0.1% by weight of the polyethylene. 15. The amount of surfactant is about 0.1 to about 0 of polyethylene.
．． 2. A method according to claim 1, wherein the amount is in the range of 2% by weight. 16. A buoyant, moisture-resistant, cold-resistant, and water-repellent low-density polyethylene sheet or tube produced by the method described in claim 1. 17. Clothing using a lining of a low-density foamed and expanded polyethylene sheet produced by the method described in claim 1. 18, thickness of about 0.5 mm to about 1 mm, buoyancy such that a weight of about 130 kg or more can be kept afloat by a 300 g sheet, and about 12 when the thickness is about 0.5 mm
g/square yard to about 21 g/ when the thickness is about 1 mm
Low density foam expanded polyethylene sheets with weights in the square yard range.