JPH06143317A - Heat resistant resin injection molded vessel and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a vessel to be molded by highly crosslinked polybutadiene from liquidlike polybutadiene resin without lowering coloring, transparency within a relatively short time and a heat resistant resin injection molded vessel having excellent noncoloring properties or transparency, thermal deforming temperature, and thermal decomposing temperature in combination. CONSTITUTION:A heat resistant injection molded resin vessel is formed by injection molding and curing a resin composition containing liquidlike polybutadiene including 1,2-butadiene unit and radical initiator of catalytic amount in a polymer chain in such a manner that the chain is highly crosslinked through a vinyl group of 1,2-butadiene unit and has a thermal deforming temperature of 220 deg.C and a thermal decomposing temperature of 450 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant resin injection-molded container having excellent transparency and a method for producing the same, more specifically, a combination of excellent heat resistance and mechanical properties such as impact resistance. The present invention also relates to a heat-resistant resin injection-molded container having excellent flavor retaining property for contents even when heated at a high temperature by direct fire or the like.

[0002]

2. Description of the Related Art Plastics have been widely used for containers because they are lighter in weight than materials such as metals and have some impact resistance.
However, plastic is generally inferior in heat resistance, and for example, in the field of packaging containers for cooking contents, in terms of heat resistance, corrosion resistance, and flavor retention during cooking. It still has some problems that must be resolved.

Generally, a typical heat-resistant resin container is made of a thermosetting resin, but many known ones have thermal decomposability to some extent and are directly decomposable. In the case of heating with fire, there is a tendency to cause decomposition that cannot be ignored and impair the flavor retention of the contents. Of course, in order to raise the thermal decomposition temperature, it is possible to introduce a high degree of cross-linking structure, but in this case, the molding container becomes mechanically brittle,
Impact resistance tends to decrease.

As a representative of different types of heat resistant containers, it is known that a surface of a metal substrate is provided with a film of fluororesin, polyimide resin or thermosetting resin. This kind of container is The resin coating must be provided on the container before or after molding, which is a drawback of complicated operation.

Recently, JP-A-2-247237 discloses that 70% of vinyl-type double bonds of polybutadiene containing 40 mol% or more of vinyl-type double bonds with respect to a monomer unit.
An ultrahigh heat resistant resin obtained by subjecting the above to a crosslinking reaction is described.

[0006]

The above-mentioned liquid polybutadiene has the advantage that it is highly crosslinkable and does not lose its toughness even after being highly crosslinked. Moreover, there is a problem that the resin after highly crosslinked is colored or loses its transparency.

Therefore, an object of the present invention is to provide a method for producing a liquid polybutadiene resin which can be molded into a container made of highly crosslinked polybutadiene in a relatively short time and without deterioration of coloring and transparency. There is.

Another object of the present invention is to provide a heat-resistant resin injection-molded container having a combination of excellent non-coloring property or transparency, heat distortion temperature and heat decomposition temperature.

[0009]

According to the present invention, in-mold injection molding of a resin composition containing liquid polybutadiene containing 1,2-butadiene units in the polymer chain and a catalytic amount of a radical initiator. And the polymer chain is highly cross-linked through the vinyl group of the 1,2-butadiene unit and has a heat distortion temperature of 220 ° C. or higher and a thermal decomposition temperature of 450 ° C. or higher. A characteristic heat-resistant resin injection-molded container is provided.

According to the invention, there is also a 1,2 in the polymer chain.
-Injecting a resin composition containing a liquid polybutadiene containing a butadiene unit and a catalytic amount of a radical initiator at a high pressure into a mold heated to a high temperature, and applying the resin composition under a high resin pressure. Provided is a method for producing a heat-resistant resin injection-molded container, characterized in that the resin composition is retained in a mold and the resin composition is cured in the mold.

In the present invention, when the liquid polybutadiene composition is injected, the resin composition is injected after removing oxygen in the mold or replacing the inside of the mold with nitrogen.
Alternatively, as the injection mold, it is preferable to use one having a groove for air escape on the mating surface and to remove air in the mold to the groove for air escape by resin pressure.

[0012]

In the present invention, the liquid polybutadiene containing 1,2-butadiene unit in the polymer chain is used as a resin raw material because the 1,2-butadiene unit (that is, vinyl group) which serves for high degree of crosslinking is used. And the resin after crosslinking has excellent toughness and impact resistance.

However, liquid polybutadiene has a problem that it requires a high temperature and a considerably long time to highly cross-link it, and that molding into a container is not practical, and that the molded product tends to be colored during cross-linking. There's a problem. This is probably because the liquid polybutadiene contains a high concentration of double bonds, which easily forms a polyene structure due to oxidation or other side reactions. Such a tendency is particularly remarkable when the curing reaction for liquid polybutadiene is carried out in the presence of a radical initiator.

A resin composition containing liquid polybutadiene and a catalytic amount of a radical initiator is injected at high pressure into a mold heated to a high temperature, and the resin composition is kept in the mold while a high resin pressure is applied. It is a remarkable feature of the present invention that the resin composition is allowed to stay in the mold and is cured in the mold.

That is, according to the present invention, an injection mold heated to a high temperature is used, and the resin composition is injected into the mold,
By allowing the resin to stay in the mold while applying a high resin pressure, the molding and high-level curing of the resin can be performed within a remarkably short time without coloring or impairing transparency. Air in the mold is discharged from the parting surface to the outside of the mold by the high pressure of the resin, and the contact between the resin and oxygen is blocked, so that the coloring and the inclusion of air bubbles are prevented.

In the present invention, it has been discovered as a phenomenon that a high degree of curing of liquid polybutadiene is possible within a short period of time, and although the reason for this is not fully clear, the polymerization-curing system of the present invention is used. Then, because of the high temperature and high pressure and the wall effect of the mold surface, the generation efficiency of the polymer radicals is high, and the mobility of the polymer radicals is also high, so that the polymerization of the vinyl side chain may proceed rapidly. Seem.

Conventionally, as a resin container which can be heated to a high temperature, highly crystallized polyester and several thermosetting resin types are known, but these are all opaque or colored. It is impossible to check the cooking status of the contents through the wall. As a material having a slight transparency, there is a material made of heat-resistant glass such as pyroceram, but these are expensive and have low impact resistance, and are obviously unsuitable for use as a packaging container. On the other hand, in the present invention, it is possible to significantly improve the heat resistance by highly crosslinking 1,2-butadiene while preventing coloration or maintaining transparency.

The heat-resistant resin container of the present invention is exceptionally excellent in impact resistance as a highly crosslinked resin. The reason for this seems to be that liquid polybutadiene, even though highly crosslinked, still has the rubbery properties inherent to polybutadiene.

Since the heat-resistant resin container of the present invention has a heat distortion temperature of 220 ° C. or higher and a thermal decomposition temperature of 450 ° C. or higher, it is filled with uncooked or cooked foods, etc. Even when placed in a microwave oven, toaster oven or the like and heated, the container is not deformed and the contents are not scorched, which is extremely suitable for this purpose.

[0020]

Preferred Embodiment of the Invention

(Liquid polybutadiene) Liquid polybutadiene used in the production of the container of the present invention is a liquid polymer obtained by polymerization of butadiene.

[Chemical 1] Containing a 1,2-butadiene unit represented by

Sometimes has a at indicated are 1,4-butadiene units - ## STR2 ## _{-CH 2 -CH = CH-CH 2} .

A carbon-carbon double bond is present in these butadiene units, and due to this double bond, polymerization and cross-linking between molecules to promote polymerization and reticulation proceed. The cross-linked structure includes (1) a cross-linked structure of 1,2-butadiene units, (2) a cross-linked structure of 1,4-butadiene units, and (3) a 1,2-butadiene unit and a 1,4-butadiene unit. There is a cross-linked structure of cross-linked structure by each other,
In the 1,2-butadiene unit, the double bond is in the side chain,
The probability of crosslinking is significantly higher than that of 1,4-butadiene.

In the present invention, liquid polybutadiene containing the above-mentioned unit "Chemical formula 1" or both the units "Chemical formula 1" and "Chemical formula 2" is used for injection molding. The amount of 1,2-butadiene units and 1,4-butadiene units in the liquid polybutadiene and the presence of the crosslinked structure of the above formula in the cured molded article is
It can be confirmed by nuclear magnetic resonance (MNR). According to one example of suitable results, 60 to 95% of 1,2-butadiene units and 30 to 70 of 1,4-butadiene units.
It was in fact confirmed that% was involved in the crosslinking.

The 1,2-butadiene unit in the liquid polybutadiene is preferably present in an amount of 40 mol% or more, particularly 50 mol% or more. When the amount of 1,2-butadiene units is less than the above range, the crosslink density that can be introduced becomes small, and it tends to be difficult to obtain a predetermined heat resistance. This liquid polybutadiene is generally 500 to 10
It is preferable to have a number average molecular weight of 10,000, especially 1500 to 8000. When the liquid polybutadiene contains 1,4-butadiene units, the cured molded article becomes tougher. Therefore, it is particularly desirable to contain 1,4-butadiene units in an amount of 5 mol% or more.

The liquid polybutadiene is obtained by subjecting butadiene to a low polymerization in the presence of a 1,2-polymerization catalyst known per se so that the molecular weight falls within the above range. A suitable liquid polybutadiene is B- manufactured by Nisseki Chemical Co., Ltd.
Available as 3000.

(Molding composition) As the radical initiator, organic peroxides such as organic peroxides, organic hydroperoxides, organic peracids, azo compounds, and further 2,3
-Dicumyls such as dimethyl-2,3-dibuenylbutane can be used. Suitably, an organic peroxide such as
2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne, 2,5-dimethyl-2,5-di (t
ert-Butylperoxy) hexane, 1,3-bis (tert-butylperoxyisopropenyl) benzene, 1,1-bis (tert-butylperoxy)-
3,3,5-Trimethylcyclohexane, dicumyl peroxide, tert-butyl-cumyl peroxide and the like are used alone or in combination of two or more. These radical initiators or cross-linking agents are used in catalytic amounts, and generally, per 100 parts by weight of liquid polybutadiene,
It is preferably used in an amount of 0.05 to 10 parts by weight, particularly 0.2 to 3.0 parts by weight.

The molding composition used in the present invention may be compounded with a compounding agent known per se according to a known formulation. For example, other modifying thermosetting resins such as phenol resin, epoxy resin, amino resin, xylene resin, in an amount of generally 10 parts by weight or less per 100 parts by weight of the crosslinked product, within a range that does not impair the essence of the crosslinked product. An alkyd resin, a bismaleimide resin, a cyanuric acid ester resin, a urethane resin, a silicone resin or the like can be added.

In the present specification, the non-coloring property or transparency of the resin means that the resin itself is substantially uncolored and transparent, and the container wall is colored with another material or opaque. It is safe to say that it has been converted. Thus, this molding resin composition contains various colorants, fillers, inorganic or organic reinforcing agents, lubricants, plasticizers, leveling agents, surfactants, thickeners, reducing agents, depending on the application. A viscous agent, a stabilizer, an antioxidant, an ultraviolet absorber and the like can be added. The blending of the inorganic filler is advantageous in terms of both heat resistance and increase in amount, and in the case of a transparent or translucent container, it is 0.1% per 100 parts by weight of the resin.
To 10 parts by weight, especially 0.1 to 0.3 parts by weight, and in the case of opaque containers, 10 parts by weight per 100 parts by weight of resin.
The filler may be incorporated in an amount of 1 to 150 parts by weight, especially 10 to 30 parts by weight.

Examples of the filler include calcium carbonate, silica, silica-alumina, various clays, zeolite, talc, magnesium hydroxide, magnesium carbonate, magnesium silicate, aluminum hydroxide and gypsum.

(Injection molding) According to the present invention, the above resin composition is injected into a mold heated to a high temperature at a high pressure, and the resin composition is retained in the mold while a high resin pressure is applied. Then, the resin composition is cured in the mold. As the injection mold, it is preferable to remove oxygen in the mold or replace nitrogen in the mold prior to injection, but of course, even if such a mechanism is not provided, a mold matching surface of the injection mold, That is, by providing an air escape groove on the mating surface,
Air inside the mold can be effectively eliminated by the resin pressure. In the present invention, since the resin pressure is high, the air escape groove may have an extremely small size and a small capacity.

In FIGS. 1 and 2 showing an injection mold suitably used for the purpose of the present invention, this mold comprises a female mold 1 and a male mold 2, and a resin 3 is injected. It has a cavitation that can be done. This cavity is roughly composed of a bottom wall forming part 4, a side wall forming part 5 and a flange forming part 6. The female mold 1 is provided with a gate 7 so as to be connected to substantially the center of the bottom wall molding portion 4.

On the outer circumference of the female die 1, there are mating surfaces 8 and 8 which are sealed with respect to the male die 2 at the time of molding. Inside the mating surface 8, the flange molding part 6 is provided. On the other hand, a groove or void C having a minute gap connected to the outside is provided. The groove or the void portion C serves as a flow path for purging air or flowing an inert gas such as nitrogen before or during injection molding. The groove or void C is provided with an inlet A for supplying an inert gas such as nitrogen and an outlet B for discharging air or nitrogen.

In a preferred embodiment of the present invention, after the injection die is clamped at the time of molding, nitrogen is injected from the inlet A to purge air (oxygen) remaining in the cavity from the outlet B, and Fill the inside with nitrogen. This operation may be carried out only at the start of molding, or nitrogen may be continuously flown out until the molding operation is completed.

The surface temperature of the injection mold is such that the liquid polybutadiene to be injected can be polymerized and cured in a short time,
Generally, a temperature of 230 to 330 ° C., particularly 280 to 310 ° C. is desirable. In order to maintain the surface temperature of the injection mold within the above range, it is preferable to provide an electric heating mechanism and a temperature detection mechanism near the surface of the injection mold and automatically control the surface temperature to be constant.

The injection machine may be any known in itself.
Can be used, but the resin composition to be blended
It is preferable to have a vent mechanism for degassing the oxygen inside.
Good Change the cylinder temperature to the resin
(Higher gelation) does not occur, keep the temperature as high as possible
It is preferable that the temperature is generally 50 to 150 ° C., especially 100.
A temperature range of up to 130 ° C is suitable. Injection pressure is as high as possible
It is desirable to be large, generally 500 to 1500 kg
f / cm², Especially 900 to 1300 kgf / cm ²Range of
Is desirable.

The residence time of the resin composition in the injection mold varies depending on the temperature, the pressure, the thickness of the container, etc., and the degree of crosslinking of the resin, but it is generally 1 to 10 minutes, particularly 1.5.
To 3 minutes. When the molding container is taken out at a high temperature, it may be taken out after cooling the mold to some extent in order to prevent it from being deteriorated due to contact with air. .

After molding, the container taken out from the injection mold may be heated in an inert atmosphere such as nitrogen or in a reduced pressure atmosphere to perform post-curing or alleviate molding distortion. This post-treatment is at 230-330 ° C and 1
It can be performed for about 30 minutes.

(Molding Container) According to the present invention, the heat-resistant resin container is thus made of a resin composition containing liquid polybutadiene containing 1,2-butadiene units in the polymer chain and a catalytic amount of a radical initiator. It is formed by in-mold injection molding and in-mold curing. The resin constituting this container has a polymer chain which is highly crosslinked through a vinyl group of a 1,2-butadiene unit and has a molecular weight of 60 to 95 of a 1,2-butadiene unit.
%, And 30 to 70% of the 1,4-butadiene units are involved in crosslinking. Therefore, this container has a heat distortion temperature of 220 ° C. or higher and a thermal decomposition temperature of 450 ° C. or higher, and is extremely excellent in heat resistance.

The injection-molded resin container of the present invention comprises a tray,
It is useful as a packaging container for storing various contents in the form of plates, various cups, bowls, bowls, bowls, etc. and heating and cooking the contents prior to eating.

[0039]

【Example】

Example 1 An injection-molding die shown in FIGS. 1 and 2 was prototyped, and liquid polybutadiene was injection-molded. A is a nitrogen inlet, B is a nitrogen outlet, and C functions as both a nitrogen flow path and an air-reserving groove. Resin is B-3000 made by Nisseki Chemical
Polybutadiene (1,2 butadiene ratio 35 mol%) 1
2,3 dimethyl 2,3 diphenyl butane 3 in 100 parts by weight
A part by weight was added to obtain a resin for injection molding. The resin was preheated at 120 ° C in a preliminary tank and then injected into the mold to produce 315 ° C 12
It was held at a pressure of 00 kgf / cm ² for 100 seconds. Figure 1 at this time
Nitrogen from A was kept flowing from before injection until the container was taken out. After heating, the mold was opened and the container was taken out, and a transparent container was obtained without discoloration or cracking. When the thermal decomposition temperature was examined by thermogravimetric analysis, it was 499 ° C (Fig. 3). Measurement condition is N
_Two substitutions were performed, the heating rate was 40 ° C./min, and the on set temperature.
The heat distortion temperature was 258 ° C. (4.6).
kgf / cm ² ).

Example 2 A resin having a 1,2-butadiene ratio of 90% was used, and the same procedure as in Example 1 was used except that nitrogen was not flowed.

Example 3 A resin having a 1,2 butadiene ratio of 35% was used as a curing agent (2,
3 dimethyl 2,3 diphenyl butane) 1 part by weight,
It was manufactured using the same method as in Example 1 except that the injection mold temperature was 290 ° C.

Comparative Example 1 In Example 1, the curing agent was changed to 2,5-dimel 2,5-di (te).
(rt-butylperoxyhexyne) 3 parts by weight, and using a mold without an air-retracting groove, a container was manufactured by the same method.

Comparative Example 2 A container was manufactured by the same method as in Example 3 except that the mold holding time was 50 sec.

Comparative Example 3 A resin having a 1,2 butadiene ratio of 35% was used, 1 part by weight of 2,3 dimethyl 2,3 diphenylbutane was added, and the mold was kept at 315.degree. 220
A container was manufactured while holding sec. The results obtained in these examples are shown in Table 1.

[0045]

[Table 1]

[0046]

INDUSTRIAL APPLICABILITY According to the present invention, a resin composition containing liquid polybutadiene and a catalytic amount of a radical initiator is injected into a mold heated to a high temperature at a high pressure, and the resin composition is injected at a high pressure. Retain in the mold with the resin pressure applied,
By curing the resin composition in the mold, molding and high-level curing of the above resin can be performed within a remarkably short time without coloring or impairing transparency.

The heat-resistant resin container of the present invention is exceptionally excellent in impact resistance as a highly cross-linked resin, and is extremely suitable for a packaging container, and also contains uncooked or cooked foods as contents. Even when filled and heated in a microwave oven or oven toaster or the like, the container is not deformed and the contents are not scorched, and is very suitable for this purpose.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an injection molding die used in Example 1 of the present invention.

FIG. 2 is a top view of a female die in the injection molding die of “FIG. 1”.

FIG. 3 is a thermogravimetric analysis graph of the injection-molded resin obtained in the example.

[Explanation of symbols]

 1 Female type 2 Male type 3 Resin 4 Bottom wall forming part 5 Side wall forming part 6 Flange forming part 7 Gate 8 Mold matching surface A Gas inlet B Gas outlet C Groove or void

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Claims (4)

[Claims] 1. A polymer formed by in-mold injection molding and in-mold curing of a resin composition containing liquid polybutadiene containing 1,2-butadiene units in the polymer chain and a catalytic amount of a radical initiator. A heat-resistant injection-molded resin container, characterized in that the chains are highly cross-linked through vinyl groups of 1,2-butadiene units and have a heat distortion temperature of 220 ° C or higher and a thermal decomposition temperature of 450 ° C or higher. 2. A resin composition containing liquid polybutadiene containing 1,2-butadiene units in the polymer chain and a catalytic amount of a radical initiator is injected into a mold heated to high temperature at high pressure, and A method for producing a heat-resistant resin injection-molded container, characterized in that the resin composition is retained in a mold while a high resin pressure is applied, and the resin composition is cured in the mold. 3. The method for producing a heat-resistant resin injection-molded container according to claim 2, wherein oxygen in the mold is removed or the inside of the mold is replaced with nitrogen, and then the resin composition is injected. 4. An injection mold is used which has an air-removing groove or a void portion on a mold-matching surface, and the air in the mold is removed by a resin pressure into the air-retaining groove or nitrogen is flowed. The heat-resistant resin injection-molded container manufacturing method according to claim 2, wherein