JP2964263B2 - Manufacturing method for pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses a novel green inside paint to improve the releasability in a vulcanization molding process, improve air pressure retention, and reduce weight. The present invention relates to a method for manufacturing a pneumatic tire that can be manufactured.

[Conventional technology]

A pneumatic tire is manufactured by inserting a green tire into a mold, heating and vulcanizing the inside of the green tire while pressurizing it with a bag-shaped bladder that expands like a rubber balloon. In this case, a paint composition called green inside paint is applied to the inner surface of the green tire in order to ensure releasability between the vulcanized tire and the bladder. This paint composition is, for example, a dispersion of mica powder or talc having a relatively large particle diameter in water using a surfactant, and after vulcanization molding, remains in a particulate state on the tire inner surface, It did not improve tire performance at all.

On the other hand, on the inner surface of the pneumatic tire, an inner liner layer made of a non-gas-permeable rubber such as butyl rubber is stuck to keep the air pressure constant. However, since butyl rubber is not completely non-permeable to gas, it needs to have a rubber thickness of at least about several hundred μm in order to maintain a necessary air pressure, and this has caused an increase in tire weight.

[Problem to be Solved by the Invention] An object of the present invention is to use a novel green inside paint to ensure the releasability during vulcanization molding of a green tire by a mold, and to perform vulcanization molding. It is another object of the present invention to provide a method for manufacturing a pneumatic tire capable of forming a lightweight thin film having excellent air pressure retention.

[Means for solving the problem]

The object of the present invention can be achieved by a method of applying ultra-high molecular weight polyethylene powder to the inner surface of a green tire and then vulcanizing and molding the green tire.

Ultra high molecular weight polyethylene powder applied to the inner surface of the green tire is used as a green inside paint when the green tire is inserted into a mold and vulcanized while pressing against the inner surface of the mold by inflating the bladder. In addition to exhibiting good releasability, it can be fused to each other to form a coating and simultaneously adhere to the tire inner surface. Since this coating has a small specific gravity and has excellent non-gas permeability, it can function as an inner liner layer, so that it may be replaced with a part or all of the conventional inner liner layer made of butyl rubber. Thus, the tire can be provided with excellent air pressure retention while reducing the weight of the tire.

The molecular weight of such ultrahigh molecular weight polyethylene powder is desirably 1,000,000 or more in average molecular weight.
The upper limit is not particularly limited, but is preferably as large as possible within the range in which synthesis is possible. With such an ultrahigh molecular weight, the polyethylene powder can be adhered to the tire inner surface as a coating. In contrast,
When the polyethylene powder has a low molecular weight, it cannot be adhered even if a film is formed, or the adhesion strength is extremely low, so that the film is easily peeled off, and a film having sufficient durability cannot be formed.

The particle size of the ultra-high molecular weight polyethylene powder is not particularly limited, but 10 to 400μ, preferably 20
Those having a range of 200 μm are preferable. Particle size of 10μ or more, 400μ
A paint composition that is easy to apply can be obtained by setting the content in the following range.

In the present invention, the ultra high molecular weight polyethylene powder may be applied as it is to the inner surface of a green tire, or as a conventional green inside paint, as a paint composition suspended or dispersed in an organic solvent or water. Can also be used. The blend amount of ultra high molecular weight polyethylene powder in this paint composition is 10-40% by weight
It is preferable that In the case of an organic solvent type suspension, the remaining 60 to 90% by weight is used as an organic solvent such as gasoline for rubber. In the case of an aqueous dispersion type suspension, it is preferable to use a surfactant in combination. Specifically, the mixing ratio is preferably 10 to 40% by weight of ultrahigh molecular weight polyethylene powder, 40 to 89% by weight of water, and 0.1 to 5% by weight of a surfactant.

Further, a fine lubricant, a preservative, a rust inhibitor, a fungicide, a pigment, and the like can be added to the paint composition as desired.

In order to mix the respective components of the paint composition, it is preferable to use a paint roll, a ball mill, or the like and apply a mechanical external force to forcibly disperse the ultrahigh molecular weight polyethylene powder.

When ultra-high molecular weight polyethylene powder is used directly as an application method on the inner surface of the green tire, it can be applied by spraying on the inner surface of the tire. When used as a paint composition, it can be applied by brushing or spraying with a spray device using air pressure or liquid pressure. The coating amount of the paint composition is preferably such that the thickness of the ultrahigh molecular weight polyethylene coating is 30 to 200 μm. By setting the thickness of this coating to 30 μm or more, a coating that substitutes for the inner liner layer and has excellent strength and air pressure retention can be formed. When the thickness is 200 μm or less, the increase in rigidity of the inner surface of the tire as the inner liner layer can be reduced, and flexibility can be ensured.

When a tubeless pneumatic tire is manufactured by the method of the present invention, ultra high molecular weight polyethylene powder is
At the same time as being used as an inside paint, the coating formed on the inner surface of the tire can also function as an inner liner layer. When a tire with a tube is manufactured, the tire can also function as a protective layer of the inner liner layer. Furthermore, it can be used together with a conventional inner liner layer, but in this case,
The thickness of the inner liner layer can be reduced and the weight can be reduced.

As the vulcanization molding temperature of the green tire coated with the ultra-high molecular weight polyethylene powder as described above, a temperature equal to or higher than the melting point of the ultra-high molecular weight polyethylene powder, for example, 140 ° C. to 180 ° C.
It is desirable to keep the temperature at the same level. By vulcanizing at such a temperature, the ultrahigh molecular weight polyethylene powder can be melted, and a film can be formed and bonded at the same time.

The figure shows an example of a pneumatic tire obtained by the manufacturing method of the present invention. A carcass layer 2 which is turned up from the inside to the outside of the tire is mounted around a pair of bead cores 1 on both right and left sides. , An ultra-high molecular weight polyethylene coating F is formed.

〔Example〕

In applying green inside paint to the inner surface of a green tire having the same internal structure and vulcanizing and molding, different types of green inside paint are used as in the following Examples 1 and 2 and Comparative Example, respectively. Do 3
Ten types of pneumatic tires were manufactured. These tire sizes were the same 185 / 75R13.

Example 1: Ultra high molecular weight polyethylene powder of the blending ratio shown in the table,
After sufficiently mixing the surfactant and water with stirring, the mixture was passed through a paint roll and filtered through an 80 mesh filter to prepare a paint composition. The paint composition as a green inside paint, is applied to the inner surface of the green tire so that the amount of ultra high molecular weight polyethylene powder of about 50 g / m ^2, dried, using a mold in a conventional manner Vulcanized and molded.

Example 2: A green tire was molded and vulcanized in the same manner as in Example 1 except that a green tire having no inner liner layer was used.

Comparative Example: A talc, a sericite, a silicone emulsion, a surfactant, and water having the compounding ratios shown in the table were sufficiently stirred and mixed, passed through a paint roll, and filtered through an 80 mesh filter to prepare a paint composition. This paint composition was applied as a green inside paint to the inner surface of a green tire and then vulcanized.

Each of these three types of tires exhibited good releasability, and no product failure occurred.

About these three types of tires, the weight was measured and the following air leak test was performed.

Air leak test: After mounting the tire (stationary state) on a standard rim at a room temperature of 21 ° C, the tire was left at an internal pressure of 2.0 kg / cm ² for 48 hours, and the internal pressure was 2.0 kg / cm ^2.
Readjust to The internal pressure is measured over a period of three months every 48 hours after the readjustment as a starting point of the measurement start time.

The measured data is regressed to y = exp (-βt) by the least squares method, y = internal pressure (measured internal pressure / 2.0), t = time (days)
To determine the air leak coefficient β.

Substituting t = 30 days, the internal pressure decrease rate (Z) per month is calculated according to the following equation.

Z (% / month) = [1−exp (−β · 30)] × 100 The measurement results are shown in the table below.

As shown in the table, the tire of Example 1 has substantially the same weight as the tire of the comparative example,
It can be seen that the air pressure retention is significantly improved. Also,
The tire of Example 2 is significantly lighter in weight than the tire of Comparative Example, and has excellent air pressure retention.

Also, the releasability of the tire in the method of the present invention was not different from the conventional method. Moreover, the inner surface of the product tire is smooth, and the hands and floor of the worker are not contaminated at all by the falling off of the particulate green inside paint adhered to the inner surface unlike the conventional tire. Was.

〔The invention's effect〕

According to the present invention, by using an ultrahigh molecular weight polyethylene powder as the green inside paint, a film having excellent mold releasability to a mold can be formed and firmly adhered to the tire inner surface. Moreover, since this coating is light and has low gas permeability, it can provide excellent air pressure retention, so that the inner liner layer can be omitted or its thickness can be significantly reduced, and the weight of the tire can be significantly reduced. It is possible to

[Brief description of the drawings]

FIG. 1 is a half sectional view showing an example of a pneumatic tire manufactured according to the present invention. 1 ... bead core, 2 ... carcass layer, F ... ultra-high molecular weight polyethylene coating.

Claims (1)

(57) [Claims] 1. A method for manufacturing a pneumatic tire, comprising applying an ultra-high molecular weight polyethylene powder to the inner surface of a green tire and then vulcanizing and molding the green tire.