JP2002254499A - Injection blow molding method for silicone rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that there is a limit in reduction of thickness in the injection molding for a condom made of a silicone rubber and it has been extremely difficult to manufacture an ultrathin-walled condom with a thickness of 0.1 mm or less. SOLUTION: An ultrathin-walled condom molded object is manufactured by manufacturing a preform product in a semicured state by the injection molding of the silicone rubber to subject the same to blow molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection blow molding method for silicone rubber, and more particularly to an injection blow molding method for an ultra-thin silicone rubber condom.

[0002]

2. Description of the Related Art Conventionally, natural rubber and polyurethane rubber have been generally used as raw materials for condoms. As a method for forming a condom using these materials, first, a vulcanizing agent such as sulfur, an auxiliary agent, or an accelerator is added to natural rubber to prepare a latex rubber as a condom raw material. An original mold made of glass or the like is immersed in this latex rubber until a desired thick film is formed, and then the original mold is pulled up, dried, wrapped, swelled and peeled, and formed by post-vulcanization. After inspection, the product is completed. In addition, the same method is used for both polyurethane and water-based polyurethane. In these immersion methods, there is a problem that the immersion liquid gathers at the tip of the original mold by gravity at the tip of the condom, so that the tip becomes thick.

[0003] In the case of natural rubber latex, rubber allergy and rubber odor are serious problems. Therefore, some polyurethane products are on the market. However, in the case of polyurethane, there are problems that the manufacturing process is complicated and mechanical properties such as elongation are inferior to natural rubber.

[0004] On the other hand, a silicone rubber injection molding method involves a polymerization degree of 50 containing an organopolysiloxane as a main component.
A silicone rubber injection molding method of a rubber composition called a millable type in which a silica-based reinforcing filler, a lubricant and various additives are blended with a linear polymer of 00 to 10000, and a linear polymer having a degree of polymerization of 100 to 2000 There is an LSR injection molding method of liquid silicone rubber (LSR) whose main component is.
In terms of fluidity, LSR injection molding having a small molecular weight and a low viscosity is favorable, and is suitable for producing thin-walled molded products.

[0005] In LSR injection molding, a two-component LSR composition is mixed at a low temperature (generally below normal temperature) in a mold cavity in which the mold temperature is set to be equal to or higher than the curing temperature of the LSR composition, and then injected and filled. Heat-cured inside to obtain a molded product. LSR
Since the composition is in the form of a low-viscosity liquid or paste before being cured, it can be injection-filled at a lower pressure than injection molding of a thermoplastic resin, a conventional millable silicone rubber or an elastomer. Also, the LSR composition is designed so that the curing reaction proceeds quickly in order to shorten the molding cycle by heat curing. Therefore, when the LSR composition is filled in the mold, it quickly cures.
Injection molded articles made of the LSR composition have a limit in thinning.

[0006] In order to produce a molded article such as a condom which is an extremely thin product, a method of reducing the viscosity of the LSR composition as much as possible to extend the flow length is conceivable. Attempts have been made to make LSR compositions. However, if the molecular weight is too low, there is a limit because the physical properties of the finally formed article are adversely affected.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a molding method capable of easily and inexpensively producing an ultra-thin silicone rubber condom which is excellent in elongation and free from rubber allergy and which is excellent in reliability. is there.

A further object of the present invention is to provide a molding method capable of producing an ultra-thin silicone rubber condom simply and inexpensively without impairing the physical properties and productivity of the molded article.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied and as a result, the molding can be facilitated by injection molding the silicone rubber composition, preforming it, and then performing blow molding. The present inventors have found that it is possible to produce an extremely thin silicone rubber condom molded product, which was difficult with the conventional method, and have reached the present invention.

That is, according to the present invention, an uncured or semi-cured silicone rubber composition is injected and filled into a mold cavity to preform a thin-walled molded product. It is intended to provide a silicone rubber injection blow molding method characterized by producing a meat condom.

[0011] The silicone rubber injection blow molding method of the present invention has, as further preferred features, "the silicone rubber composition is liquid silicone rubber" and "the male mold and the female mold of the mold cavity at the time of preform." Temperature difference "," the whole or a part of the thickness of the ultra-thin condom is 50 μm or less ", and" the silicone rubber composition dissolves a gaseous substance at normal temperature and pressure to reduce the viscosity. Injection molding and filling the silicone rubber composition into the mold cavity, and further applying pressure to prevent foaming to produce an unfoamed preform product. "

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The injection blow molding method of the present invention comprises:
It can be suitably used particularly in injection molding using an LSR composition among the silicone rubber compositions. The term "LSR composition" means any of those generally called liquid silicone rubbers, and is mainly composed of a liquid polyorganosiloxane having a reactive group, a crosslinking agent, a curing catalyst and the like. When classified according to the curing mechanism, there are a condensation reaction type, an addition reaction type, a radical reaction type, and the like. However, an addition type LSR composition is preferable from the viewpoint of a curing speed, a reaction by-product and the like.

For example, as polyorganosiloxane,
Examples of the main chain siloxane include those having a methyl group, a vinyl group, a hydroxyl group, a ketone group or the like as a functional group, and those having a vinyl group as an addition type are preferable. As the crosslinking agent, polysiloxane having a hydrogen group or the like is used.
As the catalyst, a platinum compound, an organometallic compound or the like is used. Further, the LSR composition may contain a reaction control agent, reinforcing silica, other fillers and / or additives, and the like.

[0014] In the LSR injection molding method, the A component and the B component that have become two liquids are respectively pumped up by a pump, supplied to a cylinder of an injection molding machine through a measuring device, kneaded by a screw, and then injected. , Injected into a mold, and molded by heat curing in the mold. The kneading of the two liquids may use a static mixer or a dynamic mixer depending on the material. Further, a static mixer and a dynamic mixer may be used in combination. As an injection molding machine, an in-line screw molding machine or a pre-plastic molding machine can be used as required. In the case of kneading using a static mixer, a plunger type molding machine may be used. When the LSR composition is filled into the mold cavity, the mold cavity may be previously evacuated.

Next, as one example of the present invention, an LSR injection blow molding method will be specifically described with reference to the drawings.

FIG. 1 is a schematic view showing an example of the configuration of an apparatus for molding a preform molded article according to the present invention.
FIG. 2 shows a mold part in the apparatus of FIG. 1. FIG. 2A shows a mold state at the time of preform.
(B) shows the mold open state after the preform.

In these figures, (1) is an A component material of the LSR composition, and (2) is a B component material of the LSR composition.
Component material, (3) Material supply device, (4) Material measuring device, (5) Mixing device (dynamic mixer), (6) Cylinder, (7) Male die (9) And a mold die (10), which is a female mold, for a preform, (8) a preform product, (1)
1) is a cartridge heater.

The preform product (8) is formed by first supplying a two-component A component material (1) and a B component material (2) to a measuring device (4) by a material supply device (pressurizing pump) (3). Mixing device (5) after feeding and accurately measuring materials A and B (generally 1: 1) with a measuring device
To supply. Although a dynamic mixer is shown as the mixing device (5) in FIG. 1, a static mixer may be used.

After mixing the materials A and B, an amount corresponding to the injection material is measured by the cylinder (6). At this time, the cylinder temperature is set at a temperature at which the curing reaction does not proceed, generally at room temperature or lower.
Although FIG. 1 shows an in-line screw type as the cylinder (6), it may be a plunger type.

Next, as shown in FIG.
(6) LS in the cavity of the mold (7) heated from
Injection filling of R material to produce preform product (8)
You. The mold temperature here is LSR material for preform
Need to be kept at a certain high temperature to semi-harden
There is, but if it is too hot, it will be completely cured.
In the blow molding process of the next step (Fig. 3), stretching is difficult.
Become. Specifically, the curing temperature of each LSR material is set to T
₀And the mold temperature T for the preform₁Is (T ₀
-5) C or higher, (T₀+50) ° C. or lower, more preferably
Preferably T₁Is T₀℃ or more (T₀+20) below ℃
You.

That is, since silicone rubber is a thermosetting resin, it is difficult to plasticize and deform a molded article completely cured by heating. Therefore, it is necessary for the preform to be in a semi-cured state in molding. As a method of semi-curing a molded product, it is necessary to set a specific heating temperature and a specific heating time as described above. However, a core mold (9) for injection molding and a mold ( It is also effective to apply a temperature difference to 10) to cure a part of the preform product and perform the preform. Specifically, for example, in the process of moving the molded product from the preform to the next blow molding die, when moving the preform product (8) by attaching it to the core die (9), the preform die (7) Mold temperature of the core mold (9)
The mold temperature of the mold (10) is set to (T ₀ +1) at a temperature lower than the mold temperature of ( ₀ ), for example, (T ₀ +5) ° C. or lower.
0) By setting the temperature to not less than 0 ° C., a gradient of the degree of curing occurs in one molded product.

Next, as shown in FIG. 2 (b), after the preform, the mold is opened while the preform product (8) is attached to the core mold (9), and the separately prepared blown mold shown in FIG. The mold cavity (12) for molding and the core mold (9) with the preform product (8) described above are fitted together (FIG. 3).
(See (a)) and blow molding, as shown in FIG. 3 (b), and molding of the LSR molded body in a blow mold cavity mold (12) to obtain a blow molded product (13). At this time, in order to completely cure the molded product (13), it is preferable to set the mold temperature of the blow mold cavity (12) higher than that of the core mold (9) or the mold cavity (10) for preform.
Further, at the time of blow molding, the inside of the blow molding die cavity may be evacuated if necessary.

As a silicone rubber composition other than LSR, a polymerization degree of 5,000 generally called a millable type is used.
It is composed of 10,000 linear polymers and organopolysiloxane as main components, and contains silica-based reinforcing fillers, lubricants and various additives. It is a type of rubber that is cured by adding a vulcanizing agent when used. , One-component type. Millable silicone rubber has a degree of polymerization of 100 to 200
Since the degree of polymerization is larger than that of LSR containing a linear polymer of 0 as a main component, it is difficult to produce a thin-walled molded product. However, the millable type silicone rubber is suitable for blow molding while maintaining a semi-cured state because the change in the curing rate when the temperature is increased is gentler than that of the LSR.

In the present invention, in the preform injection molding step, a gaseous substance which is a gas at normal temperature and normal pressure may be dissolved in order to reduce the viscosity of the silicone rubber composition.

As a type of the plasticizer which is blended with the silicone rubber composition to lower the viscosity, carbon dioxide is preferred, but the solubility in the silicone rubber composition is large,
It satisfies the constraints of not deteriorating the silicone rubber composition, mold, and molding machine material, not dangerous to the molding environment, being inexpensive, and quickly evaporating from the molded product after molding. If necessary, it may be a saturated hydrocarbon having 1 to 5 carbon atoms and a liquid in which hydrogen is partially substituted with fluorine, such as freon, water, and alcohol, and a mixture of two or more of these and carbon dioxide. Can be used.

When carbon dioxide is absorbed into the silicone rubber composition as a plasticizer to improve the fluidity, the silicone rubber composition contains 0.5% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more. Carbon dioxide is dissolved in the silicone rubber composition. Although there is no upper limit to the amount of dissolved carbon dioxide, if the carbon dioxide is dissolved more than necessary, it becomes easy to foam when the silicone rubber composition is filled in the mold, so the minimum carbon dioxide required to obtain the required fluidity Is preferably melted.

As the method for dissolving carbon dioxide in the silicone rubber composition, the following two methods are preferred.

One is a method in which an LSR composition or a millable silicone rubber composition is placed in a carbon dioxide atmosphere in advance, and the carbon dioxide is absorbed and then supplied into a cylinder of a molding machine. The absorption time is determined by the absorption time. In this method, it is desirable that the material supply path of the molding machine is also in a carbon dioxide atmosphere so that carbon dioxide does not escape during kneading of the silicone rubber in the cylinder.

Another method is to continuously absorb carbon dioxide before or after kneading the silicone rubber composition in a cylinder of a molding machine. Specifically, a carbon dioxide atmosphere is set immediately before the supply of the silicone rubber composition to the cylinder, or carbon dioxide is injected into the silicone rubber composition from the middle or the tip of the screw or cylinder. When carbon dioxide is injected from an intermediate portion of a screw or a cylinder, it is preferable to increase the depth of the screw groove near the injection portion and lower the pressure of the silicone rubber composition. In order to uniformly dissolve and disperse carbon dioxide in the silicone rubber composition after injecting carbon dioxide, it is preferable to attach a mixing mechanism such as a dalmage or a kneading pin to the screw or to provide a static mixer in the silicone rubber composition flow path. Further, it is preferable to install a check valve or the like as necessary so that the gas injected into the cylinder does not flow back to the material supply side. As an injection molding machine, either an in-line screw system or a screw pre-plastic system can be used.

In the present invention, before the silicone rubber composition is injected and filled into the mold cavity, it is preferable that the mold cavity is previously filled with a gas, particularly carbon dioxide. When carbon dioxide is used, for example, the amount of the gas depends on the amount of carbon dioxide that is melted into the silicone rubber composition to be injected and filled, but is preferably 0.1 MPa to 10 MPa.

In the present invention, filling the mold cavity with a gas, particularly carbon dioxide, in advance has the following two effects.

One is to fill the gas cavity into the mold cavity with a pressure equal to or higher than the pressure of carbon dioxide when dissolved in the silicone rubber composition, thereby foaming the silicone rubber composition in the mold. It is used in a method generally called counter pressure that can suppress the pressure.
The counter pressure method can prevent the formation of a foaming pattern on the surface of the molded product.However, since an excessive counter pressure hinders the filling of the silicone rubber composition into the mold cavity, select an appropriate counter pressure. Is required. The gas pressure to be sealed in the mold cavity in advance should be the minimum pressure at which the foaming pattern on the surface of the molded product disappears, and the amount of gas used in one process is minimized, and the mold cavity seal and gas supply device It is preferable that the gas pressure is low in order to simplify the structure. Gas pressure 15
If the pressure exceeds MPa, problems tend to occur such that the force for opening the mold cannot be ignored, and the sealing of the mold cavity becomes difficult.

Another effect of filling the mold cavity with carbon dioxide is that when the silicone rubber composition is filled into the mold cavity, the silicone rubber composition is filled with carbon dioxide filled in the mold cavity. The purpose of melting is to facilitate filling of the silicone rubber composition into the mold cavity and transfer of the mold surface shape. In general, as a method of improving a filling defect due to a defective gas release due to air or the like existing in a mold, a method of suctioning air in the mold in advance by a vacuum pump and setting a vacuum state in the mold is used. In the present invention, the effect can be obtained when the thickness of the molded product is extremely small. However, when a silicone rubber composition in which carbon dioxide is dissolved is filled in a mold cavity in a vacuum state, foaming occurs vigorously as soon as the mold is filled, and the appearance of a molded product may be significantly impaired. Therefore, it is preferable to fill the mold cavity with some kind of gas, and particularly preferable is carbon dioxide which is easily dissolved in the silicone rubber composition. In this case, if necessary (especially when the mold is filled with a low-pressure gas of 0.1 to 0.5 MPa, etc.), the air in the mold cavity is purged with carbon dioxide and replaced, thereby further improving the effect. Goes up.

The gas to be filled in the mold cavity in advance is not limited to carbon dioxide, but may be a simple substance or a mixture of various gases such as air and nitrogen. Very good carbon dioxide, hydrocarbons and those in which a part thereof is substituted by fluorine are preferable, and carbon dioxide is particularly preferable because it has a high effect of improving the transferability of a mold surface state to a molded article.

The method of filling the mold cavity with a gaseous substance such as carbon dioxide is extremely effective for improving the transferability of the mold cavity surface. It can also be used for normal silicone rubber injection molding that does not absorb gas.

Further, after the silicone rubber composition is first injected into the mold cavity, a secondary pressure (generally, a holding pressure, abbreviated as a holding pressure) for continuously applying a high pressure to the silicone rubber composition filled in the mold cavity. Pressure) is preferably used in combination. As a method of applying the holding pressure, a normal holding pressure for replenishing the silicone rubber composition in the mold cavity, a pressure fluid is applied to the interface between the silicone rubber composition filled in the silicone rubber composition or the mold cavity and the mold cavity interface. An external gas pressurizing method for injection or an injection compression method for reducing the mold cavity volume is used.

If the silicone rubber composition is filled into the mold cavity and cured sufficiently by the above-described method, bubbles are not generated in the molded product due to emission of carbon dioxide. On the other hand, carbon dioxide in the silicone rubber composition is gradually released into the atmosphere if the molded article is taken out into the atmosphere after the silicone rubber composition has cured.

Although the present invention is sufficiently effective in injection molding performed at a normal injection speed, the effect is further enhanced by applying high-speed injection molding which is effective for producing a thin molded article such as a material having high viscosity. High-speed injection molding means that the injection speed is 100 mm
/ Sec or more, preferably 300 mm / sec.

[0039]

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to these examples.

Example 1 First, a molding apparatus and an LSR composition used in this example will be described.

[Molding Apparatus] The molding apparatus has a configuration as shown in FIGS. 1 to 3, and a molding machine (3) used TH100R9ASELM made by Nissei Resin for LSR injection molding. This molding device has a rotating plate (not shown) that can rotate the core mold (9).

[LSR Composition] As the LSR material, W
Elastosil LR 3003 manufactured by acker
A material having a density of 1.1 and a viscosity at a shear rate of 0.9 S ⁻¹ of 200,000 mPa · s was used. LSR
The composition used was divided into A component (1) and B component (2). The A component is a platinum catalyst and the B component is a polysilyloxane having a hydrogen group as a crosslinking agent.

In this embodiment, first, a cylindrical preform molded product (8) having a root diameter of 20 mm, a length of 100 mm, and a molded product thickness of 0.10 mm was formed. Specifically, the temperature of the core mold (9) is raised to 120 ° C. and the temperature of the mold (10) is raised to 150 ° C. by heating with a cartridge heater (11) embedded in the mold (7). After setting, the LSR composition was injected and filled into the mold cavity (FIG. 2A).
Then, the LSR composition is filled in the mold cavity and 5
After curing for 2 seconds, the mold was opened while the preform molded product (8) was attached to the core mold (9) (FIG. 2).
(B)).

Next, the core mold (9) is formed by the aforementioned rotating plate.
Was rotated to move the core mold (9) to a position where it was combined with the blow mold cavity mold (12) set at 170 ° C., and then clamped (FIG. 3A). Then, pressurized gas was blown from the tip of the core mold to perform shaping (FIG. 3B).
The curing time at this time was 10 seconds. After complete curing
The mold was opened, and the blow molded product (13) was taken out.

The blow-molded product (13) obtained as described above has a root diameter of 20 mm, a length of 180 mm, a tip portion thickness of 0.03 mm, and an average thickness of 0.05 mm.
A condom-shaped ultra-thin molded product without pin poles was obtained.

(Example 2) A thin condom-shaped molded product was produced using the same material and molding machine as in Example 1. However,
As a mold for preform molding, the thickness at the time of preform molding was 0.1 mm as compared with the case of Example 1 (0.1 mm).
A mold capable of producing a thin product having a thickness of 03 mm and a thickness of 0.07 mm was used.

At the time of preform molding, the cylinder (6)
Carbon dioxide at a supply pressure of 2 MPa into the LSR
The composition was made to absorb carbon dioxide to increase fluidity. Then, after the LSR composition was primarily filled at an injection pressure of 100 MPa, a preform molded product was produced immediately by applying a secondary pressure of 40 MPa for 5 seconds.

Next, the mold is opened while the preform molded product is kept attached to the core mold (9), and the core mold (9) is rotated by the above-mentioned rotating plate, and the blow mold set at 170 ° C. After moving the core mold (9) to a position where the core mold (12) is combined with the mold (12), the mold was clamped. Next, pressurized gas was blown from the tip of the core mold to perform molding. The curing time at this time was 10 seconds. After complete curing, the mold was opened and the blow molded product (13) was taken out.

The blow-molded article (13) obtained as described above has a tip portion thickness of 0.03 mm and an average thickness of 0.3 mm.
A condom-shaped ultra-thin molded product having a diameter of 04 mm and having no pin pole was obtained.

[0050]

As described above, according to the present invention,
By blowing a pressurized gas into a semi-cured thin silicone rubber preform to produce a condom, it is possible to easily provide an ultra-thin condom that is excellent in elongation and free of rubber allergy and excellent in reliability.

In particular, a silicone rubber composition whose viscosity has been reduced by dissolving a gaseous substance at normal temperature and pressure is injected into the silicone rubber composition and injected into a mold cavity, and the pressure is further reduced so as not to foam. By producing an unfoamed preform product, the fluidity of the silicone rubber composition during molding can be kept extremely high, and the ultra-thin wall of a product having good appearance without impairing the physical properties and productivity of the molded product A silicone rubber condom can be provided simply and inexpensively.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a molding apparatus used in an embodiment of the present invention.

FIG. 2 is a view showing a mold part in a preform process.

FIG. 3 is a view showing a mold part in a blow molding step.

[Explanation of symbols]

 Reference Signs List 1 A component material 2 B component material 3 Material supply device 4 Material measuring device 5 Dynamic mixer 6 Cylinder (molding machine) 7 Mold 8 Preform product 9 Core mold (common for preform and blow molding) 10 Mold metal for preform Mold 11 Cartridge heater 12 Cavity mold for blow molding 13 Blow molded product

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // B29K 19:00 B29L 31:48 B29L 31:48 A61F 5/43 F term (reference) 4C098 AA05 DD22 EE07 EE11 4F201 AA45 AC05 AC06 AH64 AR06 AR12 BA03 BC01 BC12 BC21 BD06 BM05 BM14 4F208 AA45K AC05 AC06 AH64 AR06 AR12 LB01 LG01 LG11 LG28 LG42

Claims (5)

[Claims] An uncured or semi-cured silicone rubber composition is injected and filled into a mold cavity to preform a thin molded product, and then a pressurized gas is blown into the preformed product to form an ultra-thin condom. A silicone rubber injection blow molding method characterized by being produced. 2. The method according to claim 1, wherein the silicone rubber composition is a liquid silicone rubber. 3. The silicone rubber injection blow molding method according to claim 1, wherein a temperature difference is provided between the male mold and the female mold of the mold cavity during preform. 4. The ultra-thin condom according to claim 1, wherein the whole or a part of the thickness of the condom is 50 μm or less.
The silicone rubber injection blow molding method according to any one of the above. 5. A silicone rubber composition having a reduced viscosity by dissolving a gaseous substance at ordinary temperature and pressure into a silicone rubber composition is injected into a mold cavity, and further pressure is applied to prevent foaming. The method for injection-molding silicone rubber according to any one of claims 1 to 4, wherein an unfoamed preform is produced.