JP2002036245A - Gas vulcanization method for elastomer article and tire by this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the generation of a bare and also of an adhesive failure between tire members. SOLUTION: A pressurizing step U and a pressure lowering step D are alternately repeated during the supply of a heating medium 2A or pressurizing by a pressure medium 2B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas vulcanization method for an elastomer article, which can be suitably used for vulcanization molding of an elastomer article, particularly a rubber tire for a vehicle, and can suppress the occurrence of bears and improve the quality of the product. The method relates to a rubber tire.

[0002]

2. Description of the Related Art Vulcanization molding of an elastomer article, for example, a rubber tire for a vehicle, conventionally comprises a heating medium composed of a high-temperature gas having a high heat capacity as steam and a high-pressure gas having a low heat capacity as an inert gas such as nitrogen gas. A gas vulcanization method using a pressurized medium is widely used. This method is illustrated in FIG.
(A) and (B), a heating step s1 of heating the tire by supplying the heating medium having a predetermined temperature and pressure to an internal space c of the tire b loaded in the mold a, Then, a pressurizing step s2 of supplying the pressurized medium having a higher pressure than the heating medium to the internal space c of the tire b to pressurize, and pressing the tire b against the mold a to form the tire b. The symbol f in the figure is a bladder.

At this time, in the heating step s1, conventionally,
From the initial heating pressure p1d (0 kPa) to the highest heating pressure p1u
(About 1500 kPa), and heating is performed under this heating maximum pressure p1u (constant) until the tire reaches the vulcanization temperature (about 140 ° C. or higher). The total time t1 in the heating step s1 is about 5 to 10 minutes, and the boosting time t1a is about 15 to 30 seconds.

In the pressurizing step s2, the heating maximum pressure p1u is increased to the maximum pressurizing pressure p2u (about 2100 kPa) as an initial pressurizing pressure p2d, and vulcanization molding is completed while maintaining the vulcanization temperature. Until the pressurization is performed, the pressurization is performed under the pressurized maximum pressure p2u (constant). Pressing process s
2, the total time t2 is about 10 to 15 minutes, and the boosting time t2a is about 7 to 15 seconds.

[0005]

On the other hand, in the vulcanization molding of the tire b, due to insufficient rubber flow, the rubber g is completely contained in the concave portion d of the mold surface a1 as shown in FIG. And the quality of the product is impaired due to the occurrence of bears on the tire surface.

For this purpose, conventionally, as shown in FIG. 8 (B), a large number of vent holes e for exhausting excess air in the concave portion d are formed in the mold a to improve the rubber flow. I have. However, since the vent hole e causes even the rubber g to flow out after the exhaust, the rubber outflow remains as many spews on the tire surface after vulcanization. As a result, a great deal of effort is required to remove this spew in the tire finishing process.

Therefore, the present inventor focused on the gas vulcanization method and conducted research. As a result, in the conventional gas vulcanization method, the pressurization in the heating step s1 and the pressurizing step s2 is performed statically under a constant pressure (maximum pressure).
It has been clarified that the effect of pushing the rubber g into the concave portion d is inferior and that a bear is easily generated. When the pressure is increased and decreased alternately and the pressure is dynamically increased, the rubber g
It has been found that a bumping (collision) effect of causing the metal to collide with the mold a occurs, and the effect of pushing the metal into the recess d can be significantly improved.

That is, in the present invention, the effect of pushing rubber into the concave portion can be improved, and the number of vent holes can be reduced, based on the fact that the pressure step and the pressure step are alternately repeated in the heating step or the pressure step. It is an object of the present invention to provide a method for vulcanizing an elastomer article that can suppress the occurrence of bears while aiming.

[0009]

In order to achieve the above object, the invention of claim 1 of the present application provides a heating medium made of a gas having a high heat capacity and a high temperature into an elastomer article loaded in a mold. A heating step of heating the elastomer article, and a gas vulcanizing method for the elastomer article having a pressurizing step of pressing the elastomer article after the heating step and pressing it against a mold, wherein the heating step or the pressing step A gas vulcanization method for an elastomer article, wherein a pressure step and a pressure step are alternately repeated in the meantime.

According to a second aspect of the present invention, the pressurizing step is performed by supplying a pressurizing medium comprising a gas having a low heat capacity and a high pressure into the interior of the elastomer article after supplying the heating medium in the heating step. It is characterized by being performed.

According to a third aspect of the present invention, the step of decreasing the pressure in the heating step is to decrease the pressure from the highest pressure P1U in the step of raising the pressure to a lower limit pressure P1D equal to or less than 1/2 times the maximum pressure P1U. In addition, in the invention according to claim 4, the step of decreasing the pressure in the heating step is performed by subtracting the maximum pressure P1U from the maximum pressure P1U in the pressure increasing step.
The pressure is reduced to a lower limit pressure P1D which is greater than / 2 times, and in the invention according to claim 5, the pressure reduction step in the pressurizing step is the maximum pressure P2U in the pressure increasing step.
, The pressure is reduced to a lower limit pressure P2D equal to or less than the value of {P1U + 0.5 (P2U-P1U)}.

According to a sixth aspect of the present invention, one time Tu of the step-up step is 60 seconds or less, and one time Td of the step-down step is 60 seconds or less. Then, one time Tu of the boosting step
Is 0.5 to 10 seconds, and one time Td of the step-down step
Is 0.5 to 10 seconds or less.

In the present invention, the number Nu of the step-up steps and the number Nd of the step-down steps are each 5
The number of boosting steps Nu and the number of stepping-down steps Nd are 2 to 10, respectively.

According to a tenth aspect of the present invention, the elastomer article is a tire, and is manufactured by the method according to any one of the first to eighth aspects.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will now be described.
The case of vulcanizing an elastomeric article, for example, a vehicle tire J, will be described with reference to the illustrated examples.

As shown in FIGS. 1, 2 and 3, in the gas vulcanization method of the present invention, a heating medium 2A is supplied to the inside of a tire J loaded in a mold 3 (shown in FIG. 4). A heating step S1 for heating the tire J to the vulcanization temperature; and a pressing step S2 for supplying the pressurized medium 2B into the inside of the tire J to press the tire J and press it against the mold 3 after the heating step S1. Equipped.

In the gas vulcanization method, while the heating medium 2A is being supplied (that is, during the heating step S1) or during pressurization by the pressurizing medium 2B (that is, during the pressing step S2). The main feature is that the step-up step U and the step-down step D are alternately repeated.

Here, the heating medium 2A is made of a high-temperature gas having a high heat capacity, that is, a steam in the form of saturated steam, and is higher than the vulcanization temperature (about 140 ° C.), for example, 200 ° C., as in the prior art.
High temperature of about ゜ C and supply pressure PA of about 1500 kPa
From the heating medium supply source 4 (shown in FIGS. 4 and 5). The pressurized medium 2B is made of a high-pressure gas having a low heat capacity such as an inert gas, usually nitrogen gas, and is usually higher than the supply pressure PA of the heat medium 2A, for example, 2100.
It is supplied from the pressurized medium supply source 5 under a supply pressure PB of about kPa.

The pressure medium 2B is usually supplied at a low temperature of about 40 ° C. However, as shown in FIG. 3, when performing the pressure fluctuation of the pressure increase and the pressure decrease in the pressurizing step, the pressure is supplied at a high temperature of about 160 ° C. which is equal to or slightly higher than the vulcanization temperature.
It is preferable in order to eliminate the adverse effect on the vulcanization due to the pressure fluctuation of the pressure increase and decrease. The heating medium 2A and the pressure medium 2B
May be collectively referred to as a vulcanization medium 2.

As shown in FIG. 4, the mold 3 includes, for example, an upper mold 3U and a lower mold 3L which can be separated vertically, around a center mechanism 6 concentric with the tire shaft. The splitting surface of the lower mold 3L abuts to form a vulcanizing chamber 7 for loading the tire, which has the contour of the finished tire J. The center mechanism 6 has an inlet 9 and an outlet 10 for sucking and discharging the vulcanizing medium 2 into and out of the vulcanizing chamber 7, respectively. A rubber bag-shaped bladder 11 for preventing direct contact with the bladder is mounted. In some cases, the bladder 11 can be removed.

A heating pipe 12A for performing the heating step S1 by supplying a heating medium 2A from the heating medium supply source 4 to the vulcanizing chamber 7, and a pressure medium supply source 5 The pressurizing pipe 12B that performs the pressurizing step S2 by supplying the pressurizing medium 2B to the vulcanizing chamber 7
Are connected.

In FIG. 4, reference numerals 30A and 30B denote exhaust pipes connected to the exhaust port 10.
A vacuum is connected to A. The vacuum 31 folds the bladder 11 by applying a negative pressure when removing the vulcanized tire from the mold 3. Reference numeral 32 indicates an on-off valve.

FIGS. 1 and 2 show that the gas vulcanization method according to the present invention employs a pressure increasing step U during the heating step S1.
1 illustrates a “time-pressure” relationship in the case of heating / transformation in which step 1 and step-down step D1 are repeated.

In these embodiments, a first pressure increasing step U0 for increasing the pressure from the initial heating pressure of 0 kPa to the maximum heating pressure P1U is performed. Thereafter, a step-down step D (D1) in which the pressure is reduced from the maximum heating pressure P1U to the lower limit pressure P1D, and the maximum heating pressure P1 is reduced from the lower limit pressure P1D.
The pressure increasing step U (U1) in which the pressure increases to U is alternately and sequentially repeated.

In the embodiment shown in FIG. 1, the maximum heating pressure P1U coincides with the supply pressure PA of the heating medium 2A, for example, 1000 to 1900 kPa, preferably 1200 kPa.
〜1700 kPa, and in this example, about 1500 kPa. Further, the lower limit pressure P1D is 1/1 of the highest pressure P1U.
It is at least 2 times, preferably about 0.6 to 0.8 times, and in this example, about 1000 kPa.

Further, one time T of the boosting step U1
u and one time Td of the step-down step D1 are 60
Seconds or less are preferred. If these times Tu and Td are too short,
The rubber flow cannot follow the bumping caused by the pressure fluctuation, and the effect of pushing the rubber into the concave portion d of the mold 3 is reduced. On the other hand, if the length is too long, the bumping action itself will not be sufficiently exhibited, and similarly, the effect of pushing the rubber will be reduced. Therefore, the times Tu and Td are preferably 10 to 4
About 0 seconds, more preferably in the range of 0.5 to 10 seconds,
It can be set to about 5 seconds.

Further, the lower limit pressure P1D is set to one of the highest pressure P1U.
When the pressure fluctuation is in a small range by setting it to be at least ２ times or more to 乃至 times or more, the rubber push-in property due to the bumping action can be exhibited by repetition, and the workability is excellent and practical. There was found.

The number Nu of the step-up step U1 and the number Nd of the step-down step D1 are each preferably 50 or less, and if it exceeds 50 times, the total time T1 of the heating step S1 is reduced.
Is excessive, wasting time, labor, costs, etc., and invites the risk of over-vulcanization. Further, since the total time T2 of the pressing step S2 is relatively reduced, the molding accuracy tends to be deteriorated. Therefore, the number is preferably not more than 30 times, and more preferably about 2 to 10 times. The numbers Nu, N
The lower limit value of d varies depending on the shape of the tread pattern of the tire J, such as the shape, depth, and complexity of the concave portion d. However, in the case of a normal tread pattern, bear can be prevented by about 5 times or less.

Although the total times T1 and T2 are not particularly limited, the total times T1 and T2 are the same as those of the first boosting step U1.
The total time T1 of the heating step S1 including u is generally 2 to
10 minutes, usually about 3 to 4 minutes, the total time T2 of the pressurizing step S2 including the final evacuation time Te is generally 4 to 15 minutes,
Usually about 6 to 9 minutes. The heating step S1 can include a constant pressure step F for keeping the pressure constant, and the constant pressure step F is preferably １ ／ or less of the total time T1.

The pressurizing step S2 in the embodiment of FIGS.
In the same manner as before, the maximum heating pressure P1U is used as the initial pressurizing pressure, and the pressure is increased at once to the maximum pressurizing pressure P2U.
Until vulcanization molding is completed while maintaining the vulcanization temperature, static pressurization is performed under a constant pressure (pressurized maximum pressure P2U). In this example, the maximum pressurized pressure P2U is equal to the pressure medium 2
For example, 1800 to 2500 which matches the supply pressure PB of B
kPa, and 2100 kPa in this example. Note that the pressure is usually higher than the heating step S1.

Next, in the method shown in FIG. 2, the heating maximum pressure P1U is, in this example, the supply pressure PA of the heating medium 2A.
For example, the case of 1500 kPa that matches the above is exemplified. In addition, the lower limit pressure P1D is equal to or less than 倍 of the maximum pressure P1U, and further, is equal to or less than ３ of the maximum pressure P1U. It should be noted that the degree described in FIG. 1 can be selected as the pressure range. One time Tu of the step-up step U1, one time Td of the step-down step D1, the number Nu of the step-up step U1, the number Nd of the step-down step D1, and the total times T1 and T2 are the same.

The lower limit pressure P1D is set to one of the highest pressure P1U.
By making it less than / 2 times or smaller, pressure fluctuation becomes large, bumping action is enhanced, rubber can be pushed efficiently, and accuracy of the elastomer article can be improved.
However, it is easy to increase the load acting on the device,
In addition, it is necessary to increase the precision of the apparatus, and the equipment cost tends to increase. Therefore, the lower limit pressure P1D is selected as occasion demands.

Next, as shown in FIG. 3, the case of the gas vulcanization method of the present invention in which the pressure step U2 and the pressure step D2 are repeated during the pressurizing step S2 will be described.

In the gas vulcanization method of FIG. 3, the heating step S1
Is performed under a constant pressure as in the related art. Specifically, the pressure is increased at a stretch from the initial heating pressure of 0 kPa to the maximum heating pressure P1U, and then statically increased under a constant pressure (maximum heating pressure P1U) until the tire reaches the vulcanization temperature. Done. The heating maximum pressure P1U is the heating medium 2A
1000 to 1900 k, which matches the supply pressure PA of
Pa, preferably 1200 to 1700 kPa, and in this example, about 1500 kPa. The lower limit pressure P1D
Is at least 1/2 times the maximum pressure P1U, preferably 0.1 times.
It is about 6 to 0.8 times, and in this example, about 1000 kPa.

In the pressurizing step S2, first, a first pressure increasing step U (U2) is performed in which the maximum heating pressure P1U is increased to the maximum applied pressure P2U as an initial pressure. Thereafter, a pressure reduction step D (D3) in which the pressure decreases from the maximum pressure P2U to the lower limit pressure P2D, and a pressure increase step U in which the pressure increases from the lower limit pressure P2D to the maximum pressure P2U.
(U3) are alternately and sequentially repeated.

Here, the lower limit pressure P2D is given by ΔP1U +
0.5 (P2U-P1U)} or less is preferable for enhancing the bumping effect. In this example, the maximum heating pressure P
The case of 1500 kPa which is equal to 1 U is illustrated.

In addition, one time T of the boosting step U3
u and one time Td of the step-down step D3, the number Nu of the step-up step U3, and the number Nd of the step-down step D3, the total time T1, T2 and the like can be set in the same manner as in FIG. In view of the fact that vulcanization has progressed to some extent, the bumping effect should be enhanced as compared with the case of FIGS.

Although the total times T1 and T2 are not particularly limited, the total time T1 of the heating step S1 including the boosting time Tu of the first boosting step U2 is generally 2 to 10 as in FIGS. Minutes, usually about 3 to 4 minutes, the total time T of the pressurizing step S2 including the final evacuation time Te.
2 is generally about 4 to 15 minutes, usually about 6 to 9 minutes.

When the lower limit pressure P2D is ΔP1U + 0.5
When (P2U-P1U)｝ is larger, the pressure fluctuation is small, and although the bumping effect is reduced and the rubber indentation effect is inferior, the device can be simplified and this is applied when a large pumping effect is not required. You can choose.

As described above, in the gas vulcanization method of the present invention,
During the heating step S1 or during the pressurizing step S2, a pressure change is performed in which the step-up step U and the step-down step D are alternately repeated.

Since this pressure fluctuation causes a bumping (collision) effect of causing the rubber to collide with the mold 3, FIG.
As shown in (A), the rubber g can be effectively pushed into the concave portion d of the mold 3 and the occurrence of bears can be suppressed. As shown in FIG. 6 (B), the bumping action is to disperse or extrude air 22 trapped between members 20, 21 such as between the inner liner and the carcass ply during formation of a green tire. It also has an effect and can greatly contribute to suppression of adhesion failure between members due to the residual air.

Since the heat of vulcanization is mainly transmitted from the mold 3, the rubber softens from the outer surface of the tire. Therefore, even in the case of the heating / transformation, the indentation effect functions sufficiently,
The occurrence of bears can be suppressed.

FIG. 5 shows an example of the pressure varying means 14 which alternately repeats the step-up step U and the step-down step D. In this embodiment, the pressure fluctuation means 14 includes a pressure sensor 15 for detecting the pressure in the vulcanizing chamber 7 and a heating pipe 12A.
(In the case of heating / transformation) or an electromagnetic switching valve 16 interposed in the pressurizing pipe 12B (in the case of pressurizing / transformation), and a control means 17 which receives the signal from the pressure sensor 15 and switches the electromagnetic switching valve 16 Consists of

The pressure sensor 15 detects when the pressure in the vulcanizing chamber 7 reaches the heating maximum pressure P1U and the lower limit pressure P1D, respectively, in the case of heating / transformation. Detects when the pressure in the vulcanizing chamber 7 has reached the maximum pressurized pressure P2U and the minimum pressurized pressure P2D, respectively. The control means 17 receives a detection signal from the pressure sensor 15,
The spool valve 16A of the electromagnetic switching valve 16 is switched alternately.

The electromagnetic switching valve 16 connects the suction port 9 to the heating medium supply source 4 (for heating / transformation) or the pressurized medium supply source 5 (for pressurization / transformation) and the exhaust pipe. 19
Switch between and. Therefore, the pressure increasing step U is performed by connecting the suction port 9 to the supply sources 4 and 5, and the pressure reducing step D is performed by connecting the suction port 9 and the exhaust pipe 19 by switching.

The pressure varying means 14 is merely an example, and various known structures can be employed.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0048]

EXAMPLE An unvulcanized tire having a tire size of 225 / 40ZR18 was prepared using the gas vulcanization method shown in FIGS.
Vulcanized according to the specifications. Then, after vulcanization molding, the incidence of poor vulcanization was compared with that of the conventional method.

<Vulcanization Insufficiency> For 1,000 vulcanized tires, the occurrence of bears on the outer surface of the tire and the occurrence of adhesion failure between members due to residual air were visually observed and the tire was disassembled.

[0050]

[Table 1]

As shown in Table 1, it can be confirmed that in the vulcanization method of the example, the vulcanization failure was greatly reduced.

[0052]

As described above, in the gas vulcanization method for an elastomer article of the present invention, since the pressure step and the pressure step are alternately repeated in the heating step or the pressing step, the rubber indentation effect is obtained. And the occurrence of bears and the occurrence of poor adhesion between tire members can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a “pressure-time” relationship in an embodiment of the gas vulcanization method of the present invention.

FIG. 2 is a diagram showing a “pressure-time” relationship in another embodiment of the gas vulcanization method of the present invention.

FIG. 3 is a diagram showing a “pressure-time” relationship in still another embodiment of the gas vulcanization method of the present invention.

FIG. 4 is a diagram conceptually illustrating a mold.

FIG. 5 is a diagram showing an example of a pressure fluctuation unit.

FIGS. 6A and 6B are cross-sectional views illustrating effects of the present invention.

FIGS. 7A and 7B are diagrams illustrating a conventional gas vulcanization method.

FIGS. 8A and 8B are diagrams illustrating a conventional problem.

[Explanation of symbols]

 2A Heating medium 2B Pressurizing medium 3 Mold U, U1, U2, U3 Step-up step D, D1, D2, D3 Step-down step

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // B29K 21:00 B29K 21:00 105: 24 105: 24 B29L 30:00 B29L 30:00 C08L 21:00 C08L 21 : 00 F-term (reference) 4F070 AA04 GA07 GC01 4F202 AA45 AH20 AM32 AR02 AR11 AR19 CA09 CA21 CB01 CL09 CN01 4F203 AA45 AH20 AM32 AR02 AR11 AR19 DA03 DA11 DB01 DC01 DL10 4F204 AA45 AH20 AM32 AR02 AR11 AR19 FA01 FA18 F01

Claims (10)

[Claims] 1. A heating step of supplying a heating medium composed of a gas having a high heat capacity and a high temperature into an elastomer article loaded in a mold to heat the elastomer article, and pressurizing the elastomer article after the heating step. A gas vulcanizing method for an elastomeric article having a pressing step of pressing against a mold, wherein the heating step or the pressing step alternately repeats a pressure increasing step and a pressure decreasing step. Gas vulcanization method. 2. The pressurizing step is performed by supplying a pressurizing medium comprising a gas having a low heat capacity and a high pressure into the inside of the elastomer article after supplying the heating medium in the heating step. The method for gas vulcanizing an elastomer article according to claim 1. 3. The pressure reducing step in the heating step, wherein the pressure is reduced from a maximum pressure P1U in the pressure increasing step to a lower limit pressure P1D which is equal to or less than 1/2 of the maximum pressure P1U. A gas vulcanization method for an elastomer article. 4. The pressure reducing step in the heating step, wherein the pressure is reduced from the maximum pressure P1U in the pressure increasing step to a lower limit pressure P1D which is larger than 1/2 of the maximum pressure P1U. A gas vulcanization method for the elastomer article according to the above. 5. The step of lowering the pressure in the pressurizing step is as follows: from the highest pressure P2U in the step of increasing the pressure to ΔP1U + 0.5
4. The gas vulcanization method for an elastomer article according to claim 1, wherein the pressure is reduced to a lower limit pressure P2D equal to or less than (P2U-P1U) １. 6. A time Tu for one step of the boosting step is 60.
The gas vulcanization method for an elastomer article according to any one of claims 1 to 4, wherein a time Td of one second or less and a time Td of one pressure reduction step are 60 seconds or less. 7. A time Tu for one step of the boosting step is equal to 0.1.
5 to 10 seconds, and the time Td for one step of the step-down step is 0.1.
The gas vulcanization method for an elastomer article according to any one of claims 1 to 5, wherein the time is 5 to 10 seconds or less. 8. The gas vulcanizing method for an elastomer article according to claim 1, wherein the number Nu of the pressure increasing step and the number Nd of the pressure decreasing step are 50 or less, respectively. 9. The gas vulcanizing method for an elastomer article according to claim 1, wherein the number Nu of the pressure increasing step and the number Nd of the pressure decreasing step are 2 to 10, respectively. 10. The elastomeric article is a tire,
A tire manufactured by the method according to claim 1.