JPS6054173B2 - Method for producing flame-retardant styrenic resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a flame-retardant styrenic resin foam.

Foams made of styrene resin are already known;
Also, its manufacturing method is also known.

The manufacturing method involves putting styrene resin into an extruder, heating and softening the resin within the extruder, and adding volatile hydrocarbons,
For example, there is a method in which butane or propane is press-injected to form a foamable resin, which is then extruded from an extruder and foamed.
This method is extremely advantageous because molded bodies having a constant cross-sectional shape, such as sheets or boats, can be easily produced all at once. Furthermore, the foams made in this way are lightweight, have high heat insulating properties, and have high strength, so they are widely used for heat insulating materials, packaging materials, and the like. However, as styrene resin foams have become more widely used, their shortcomings have become acutely apparent.

The drawback is that styrenic resins are easily flammable. Therefore, attempts have been made to make styrene resin flame retardant. The attempt is to make the styrenic resin flame retardant by mixing phosphorus or a halogen compound with the styrenic resin. However, the phosphorus or halogen compounds that have been proposed so far have no effect unless they are mixed in a certain amount, and if they are mixed in a large amount, they not only deteriorate the physical properties of the styrenic resin, but also cause excessive The drawback was that it was expensive. On the other hand, vinyl chloride resin is known as a chlorine compound.

However, vinyl chloride resin is said to be incompatible with styrene resins such as polystyrene, and therefore it is not possible to mix the two to form a uniform composition.
However, this inventor discovered that when a hydrocarbon or halogenated hydrocarbon is mixed into the styrene resin as a foaming agent, the "foaming agent" helps the mixing, and the hard vinyl chloride resin It was confirmed that it is easy to mix with

In addition, since the hard vinyl chloride resin is a resin that easily decomposes when heated, the inventor used a separate extruder to mix the two resins. It was confirmed that it is necessary to soften the material by heat and then press-fit the styrene resin into the material. Furthermore, the inventor believes that the blowing agent-containing resin mixture thus obtained is
It was confirmed that the foam foamed well and the resulting foam was flame retardant. This invention was made based on such confirmation. This invention uses a styrenic resin containing a volatile hydrocarbon or a oxidized hydrocarbon,
The foamed resin is softened in an extruder, and the hard vinyl chloride resin is heated in another extruder to produce a softened product, and the foamed resin is converted into a softened product of the hard vinyl chloride resin in the extruder. The present invention relates to a method for producing a flame-retardant styrenic resin foam, which comprises press-fitting the foam into a foam, thoroughly kneading a mixture of both resins, extruding the foam from an extruder, and foaming the foam.

An example of implementing the method of the present invention will be described below with reference to the drawings and the apparatus used therein.

The figure is a cutaway schematic representation of the apparatus used in the method of this invention. In the figure, a is a single-screw extruder, b is a two-screw extruder,
The tip of extruder a is connected to the middle of extruder b.

1 is a hopper of extruder a, from which styrene resin is charged, transported forward by a screw 3, and kneaded between the screw 3 and the barrel 2, and a heating device attached around the barrel 2. 4.

When the styrene resin is softened by heating, a blowing agent is press-fitted from the inlet 5. In this way, a softened product of the foamable resin is produced, and this is sent to the connecting vibe 6. On the other hand, in the extruder b, hard vinyl chloride resin is charged from the hopper 7, transported forward by two screws 8 and 9, and kneaded between these screws 8 and 9 and the barrel 10. Heating device 1 attached around barrel 10
1, it gets heated up.

A connecting vibrator 6 is connected to the middle of the barrel 10.
Therefore, when the hard vinyl chloride resin is softened by heating, the softened foamable resin sent from the connecting vibrator 6 is press-fitted into the hard vinyl chloride resin. The mixture of both resins thus obtained is thoroughly kneaded by screws 8 and 9, and then extruded from extruder b. The extruded mixture foams and a foam is obtained. The foam can be formed into various cross-sectional shapes depending on the nozzle attached to the tip of the extruder b. The foam thus obtained becomes increasingly flame retardant as the content of vinyl chloride resin increases.

Moreover, since vinyl chloride resin itself is used as a synthetic resin for various purposes, it is much cheaper than conventional flame retardants, and is also an excellent material for forming molded objects. ing. ``In this way, the method of this invention is excellent in that a foam that is flame retardant and has excellent physical properties can be easily obtained at a low cost.Next, various matters in the method of this invention will be explained one by one. do.

As the blowing agent, volatile hydrocarbons or halogenated hydrocarbons are used.

Volatility refers to the property that it has a boiling point lower than the softening point of styrene resin, and therefore evaporates at normal pressure when heated to the softening temperature of styrene resin. As the volatile hydrocarbon, for example, propane, butane, pentane, hexane, mixtures thereof, petroleum ether, etc. can be used. In addition, examples of volatile hydrocarbons include methylene chloride, methyl chloride,
dichlorodifluoromethane, dichlorofluoromethane,
Monochlorodifluoromethane, trichlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, etc. can be used. As the styrene resin, polystyrene, AS resin, ABS resin, styrene-maleic anhydride copolymer, and other materials generally called modified styrene can be used. It is preferable that the above-mentioned foaming agent is press-fitted into the resin so that the proportion of the foaming agent is 3% by weight or more. As the vinyl chloride resin, not only a homopolymer of vinyl chloride alone but also a copolymer of vinyl chloride and other monomers can be used.

For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, etc. can be used. Hard vinyl chloride resin is a resin that does not contain any plasticizer, or if it does contain it, it does not contain more than 5% by weight, and when it is made into a molded object, it gives a hard molded object that can replace metal. That's what I say. A single screw extruder can usually be used to make a styrenic resin into a foamable resin.

In addition, to make foamable resin, it is convenient to press-inject a foaming agent into an extruder as shown in the figure, but it is also convenient to use styrene resin that has been impregnated with a foaming agent in advance. , this may be put into an extruder. In order to soften the hard vinyl chloride resin, it is preferable to use a two-screw extruder.

This is because the hard vinyl chloride resin is easily decomposed and its decomposition temperature and softening start temperature are close to each other, so the temperature of the resin must be maintained within an extremely narrow temperature range. In contrast, a twin-screw extruder is suitable for meeting such requirements. In other words, with a two-screw extruder, there is less internal heat generation during kneading, and even if the screw groove is deep, it is possible to avoid temperature unevenness in the resin, and it is possible to suppress decomposition due to resin stagnation. Because you can. The two screws in this extruder rotate in opposite directions and preferably rotate outward. The mixing ratio of the styrene resin and the hard vinyl chloride resin can be appropriately used within the range of 10 to 9 weight % of the former and 90 to 10 weight % of the latter. However, it is preferable that the styrene resin accounts for 60-3% by weight and the hard vinyl chloride resin accounts for 40-7% by weight. When mixing both resins, styrene resin is difficult to decompose compared to vinyl chloride resin, and since it contains a blowing agent and is somewhat plasticized, the temperature of the styrene resin should be slightly higher.
It is desirable to lower the temperature to some extent immediately before press-fitting into the vinyl chloride resin. When mixing styrene resin and hard vinyl chloride resin, it is desirable to press fit the former into the latter.

In addition, the press-fitting position should be such that the styrene-based resin is press-fitted where the hard vinyl chloride-based resin is softened by heating, and that it can still be kneaded by the twin screws even after being press-fitted. is desirable. Styrenic resin is plasticized by containing hydrocarbons or halogenated hydrocarbons, so when heating it to soften it, and then heating hard vinyl chloride resin to soften it, By kneading both resins, it is easy to form a uniform composition.

Therefore, by kneading both resins for a while in a two-screw extruder, a homogeneous composition of both resins containing a blowing agent can be obtained. Therefore, if this composition is extruded from an extruder,
Here, a foam made of a composition of both resins is obtained. Since the foam thus obtained contains vinyl chloride as described above, its flame retardance gradually increases as the content increases.

Additionally, hard vinyl chloride resin alone cannot cause foaming with volatile hydrocarbons or halogenated hydrocarbons. It can be a body. The effect is remarkable in this respect. Next, further details of the method of the present invention will be explained by giving specific examples of the method of the present invention. In specific examples, parts simply represent parts by weight. Example 1 0.1 part of liquid paraffin and 1 part of talc were thoroughly mixed with 100 parts of polystyrene resin (degree of polymerization 1300) using a blender.

This mixture is caliber 40T! r! Ii single screw extruder (L/D
= 25), and from the middle of the extruder, butane was added as a blowing agent to 100 parts of the polystyrene resin that was being heated and melted.
12 parts, and while continuously mixing with the melt, a biaxial rotary extruder with a diameter of 65wn (L/D = 15
) was press-fitted. The extrusion press-in speed at this time was 5.0k9/
It was H. On the other hand, polyvinyl chloride resin (polymerization degree 80
0) 100 parts, tribasic lead sulfate 2 parts, lead stearate 2 parts
A mixture of 1 part of montanic acid wax and 1 part of montan acid wax was mixed with the
The mixture was supplied to an extruder and heated to gel at an extrusion speed of 10.5k9/H.

From the middle of the extruder, a molten mixture of polystyrene resin and a blowing agent was press-injected from the single-screw extruder and mixed continuously. Inner diameter 5Tf0n attached to the tip of a twin screw extruder
The mixture was extruded through a cylindrical mold into a large volume of air and foamed.

This cylindrical foam has an outer diameter of 26m! n1 The apparent foaming ratio was 10.4 times, and the appearance was smooth.

The composition of this foam is 3 parts of polystyrene resin and 7 parts of polyvinyl chloride resin. When the flammability test was carried out in accordance with JISA95ll, it was found to be self-extinguishing. Comparative Example 1 Polystyrene resin (polymerization degree 130
0), polyvinyl chloride resin (degree of polymerization 800), and liquid paraffin 0.2 were placed in a blender and mixed.

Furthermore, 1.0 part of talc, 2 parts of tribasic lead sulfate, 1 part of lead stearate, and 1 part of montan acid wax were added and thoroughly mixed. This mixture was passed through a caliber 40Tsn single screw extruder (
L/D=28), and 4 parts of butane as a blowing agent was press-injected into 100 W of the resin which was being heated and melted from the middle of the extruder and mixed.

Inner diameter 5 attached to the tip of the extruder? The foam was extruded into the atmosphere through a cylindrical mold. Extrusion speed is 13k9/H
It was hot. This cylindrical foam had an outer diameter of 16 wm, an apparent foaming ratio of 3.6 times, and scratched appearance. As described above, when extrusion foaming was performed using only a single-screw extruder, the foaming ratio could not be increased and the foam became extremely brittle.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view of the apparatus used in the method of this invention.

Claims (1)

[Claims] 1 A styrene resin containing volatile hydrocarbons or halogenated hydrocarbons is softened in an extruder to form a foamable resin, and a hard vinyl chloride resin is heated in another extruder to produce a softened resin. , the flame retardant method is characterized in that the foamable resin is press-fitted into the softened hard vinyl chloride resin in an extruder, the mixture of both resins is thoroughly kneaded, and then extruded from the extruder and foamed. A method for producing styrenic resin foam.