JP2006226404A - Resin pulley - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin pulley formed of a novolac type phenol resin without needing cold storage because it is not a self-reaction type, causing little molding failure such as a filling failure or gas burn like a pulley formed of a resole type phenol resin, strong against thermal shock and excelling in dimensional stability. <P>SOLUTION: This resin pulley is formed of a resin composition containing a first novolac type phenol resin, as a base resin, having a number average molecular weight Mn<SB>1</SB>not greater than 850, and a second novolac type phenol resin having a number average molecular weight Mn<SB>2</SB>greater than 850. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin pulley used for engine parts and the like of automobiles.

  As pulleys used for automobile engine parts, etc., replacement of conventional metal pulleys with resin pulleys reinforced with reinforcing fibers such as glass fibers has been made due to recent demands for miniaturization, weight reduction, and cost reduction. Is being considered. As the base resin that becomes the basis of the resin pulley, a phenol resin is used in consideration of the dimensional stability and strength of the resin pulley. And the pulley made from a phenol resin reinforced with reinforcing fibers, such as glass fiber, has reached a characteristic sufficient as a substitute for a metal pulley in terms of the dimensional stability and strength.

In recent years, resol-type phenol resins synthesized by reacting phenol and formaldehyde in the presence of a basic catalyst or in an excess of formaldehyde have been widely used as phenol resins (for example, patent documents). 1 and 2). The resol type phenolic resin is easier to melt or flow by heating than the novolak type resin, and is suitable for injection molding. Therefore, it is difficult to cause molding defects such as poor filling and gas burn. Moreover, since the cured product that is resistant to thermal shock and excellent in dimensional stability can be formed by curing after molding, particularly when the resin pulley has an insert member such as a metal, the heat resistance of the resin pulley. The impact property can be improved and the occurrence of cracks and the like can be prevented.
JP 2002-212388 (Claim 1, columns 0002 to 0004, columns 0005 to 0007) JP 2004-92688 A (columns 0013 to 0015)

However, resol type phenolic resins are self-reactive, and in order to prevent curing due to self-reactions, refrigerated storage at a low temperature of about 5 ° C. or less is necessary, and even if refrigerated storage is performed, the curing reaction gradually Will be limited to a limited period of time,
・ It is necessary to install refrigeration equipment to store resol-type phenolic resin in the production plant of resin pulleys, which requires space and materials, and the electric power required to operate the production plant. Energy consumption increases,
・ When a resin composition containing a resol-type phenolic resin as a base resin, which is the basis of a resin pulley, is manufactured at a location different from the resin pulley manufacturing plant and transported to the manufacturing plant. , Refrigerated storage must be continued, increasing the energy required for transportation,
-As mentioned above, the resol type phenolic resin has a short usable period even if it is refrigerated, so the distance that the resin composition can be transported is limited. For example, a resin composition produced in Japan It is difficult to transport to a manufacturing plant and use it for manufacturing plastic pulleys.
There is a problem.

  The object of the present invention is a novolac type phenolic resin which is not self-reactive and does not require refrigerated storage. Another object of the present invention is to provide a resin pulley that is resistant to thermal shock and excellent in dimensional stability.

The present invention is a resin pulley comprising a resin composition containing a phenol resin as a base resin, and the phenol resin includes a first novolac type phenol resin having a number average molecular weight Mn ₁ of 850 or less, and a number average molecular weight Mn ₂ is used in combination with a second novolac-type phenolic resin in which 850 exceeds 850.
The number average molecular weight Mn ₁ of the first novolac type phenol resin is preferably 750 to 850. The number average molecular weight Mn ₂ of the second novolac type phenol resin is preferably 1050 to 1150. Further, the number average molecular weight Mn ₁ is 750 to 850 first novolak type phenolic resin P _1, and the number average molecular weight Mn ₂ a second novolac-type phenolic resin P ₂ is from 1050 to 1150, the weight ratio P _It is preferable to use at a ratio of ₁ / P ₂ = 40/60 to 67/33.

According to the present invention, as the base resin, the number average molecular weight Mn ₁ is as small as 850 or less, and the first novolac-type phenol resin that easily melts or flows by heating and the number average molecular weight Mn ₂ exceeds 850. Since it is used in combination with the second novolac type phenolic resin that can form a cured product that is resistant to thermal shock and excellent in dimensional stability, as in the case of a resin comprising a resol type phenolic resin, such as poor packing and gas burn A resin pulley that is resistant to thermal shock and excellent in dimensional stability can be provided. In addition, since both the first and second novolak type phenolic resins are not self-reactive, all the various problems associated with refrigerated storage can be solved.

Each of the resin pulleys of the present invention has a number average molecular weight Mn ₁ of 850 or less as a base resin, which is synthesized by reacting phenol and formaldehyde in the presence of an acid catalyst or in an excess of phenol. A certain first novolac type phenolic resin and a _second novolac type phenolic resin having a number average molecular weight Mn ₂ exceeding 850 are used in combination.

Among these, the number average molecular weight Mn _{1 of} the first novolak type phenol resin is limited to the range of 850 or less, when the number average molecular weight Mn ₁ exceeds 850, it depends on the first novolak type phenol resin. This is because the effect of improving the fluidity of the resin composition cannot be obtained, and defective molding such as poor filling and gas burning occurs. However, when the number average molecular weight Mn ₁ of the first novolac type phenol resin is less than 750, the second novolac type phenol resin combined with the first novolac type phenol resin is resistant to thermal shock and has excellent dimensional stability. The effect of forming an object is hindered, and the formed resin pulley may be weak against thermal shock and may have low dimensional stability. Therefore, the number average molecular weight Mn ₁ of the first novolak type phenol resin is preferably 750 or more. Note that the first novolac-type phenolic resin may be a number average molecular weight Mn ₁ is a combination of two or more kinds of novolac-type phenolic resin is 850 or less.

In addition, the number average molecular weight Mn _{2 of} the second novolak type phenol resin is limited to a range exceeding 850 because, when the number average molecular weight Mn ₂ is 850 or less, the second novolac type phenol resin is affected by thermal shock caused by the second novolak type phenol resin. This is because the effect of forming a cured product that is strong and excellent in dimensional stability cannot be obtained. In consideration of further improving this effect, the number average molecular weight Mn ₂ of the second novolac type phenol resin is preferably 950 or more, more preferably 1050 or more. However, when the number average molecular weight Mn ₂ of the second novolac phenol resin exceeds 1150, the fluidity of the resin composition is improved by the first novolac phenol resin combined with the second novolac phenol resin. This may hinder the effect of molding and cause defective molding such as poor filling and gas burn. Therefore, the number average molecular weight Mn ₂ of the second novolac type phenol resin is preferably 1150 or less. As the second novolac-type phenolic resin may be a number average molecular weight Mn ₁ is a combination of two or more kinds of novolac-type phenolic resin exceeds 850.

The first novolac type phenolic resin and the second novolac type phenolic resin may be blended in an arbitrary ratio. For example, the number average molecular weight Mn ₂ is small even within the above preferred range. In the case of using the second novolak type phenolic resin, the ratio of the second novolak type phenolic resin is set in order to sufficiently exhibit the effect of forming a cured product that is resistant to thermal shock and excellent in dimensional stability. On the contrary, when using the second novolac type phenol resin in which the number average molecular weight Mn ₂ is large even within the above preferred range, the resin by the first novolac type phenol resin to be combined is used. In order to sufficiently exhibit the effect of adjusting the fluidity of the composition to a suitable range, it is preferable to set the ratio to a small value.

Specifically, for example, a first novolac type phenol resin P ₁ having a number average molecular weight Mn ₁ of 750 or more and 850 or less and a second novolac type phenol having a number average molecular weight Mn ₂ of 950 or more and less than 1050 When the resin P ₂ is combined, the weight ratio P ₁ / P ₂ is preferably in the range of P ₁ / P ₂ = 35/65 to 65/35, and the range of 45/55 to 55/45 More preferably. The number average molecular weight Mn ₁ 750 or more, the first novolak type phenolic resin P ₁ is 850 or less, a number average molecular weight Mn ₂ is 1050 or more, the second and the novolak phenolic resin P ₂ is 1150 or less When combined, the weight ratio P ₁ / P ₂ of both is preferably in the range of P ₁ / P ₂ = 40/60 to 70/30, more preferably in the range of 50/50 to 60/40. Further preferred.

  Since the novolak type phenol resin is not a self-reactive type as described above, it is preferable to contain a curing agent in the resin composition in order to cause a curing reaction after injection molding. As the curing agent, various curing agents capable of curing the novolak type phenol resin can be used, and hexamethylenetetramine is particularly preferable. The ratio of the curing agent is preferably 12 to 20 parts by weight with respect to 100 parts by weight of the total amount of the first and second novolak type phenol resins.

  The resin composition may contain reinforcing fibers, inorganic fillers, lubricants and the like. Among these, as the reinforcing fiber, various inorganic or organic reinforcing fibers can be used, and inorganic fibers are particularly preferable. Examples of inorganic fibers include glass fibers, boron fibers, carbon fibers, silicon carbide fibers, alumina fibers, inorganic whiskers, and the like. In particular, glass fibers are easy to manufacture and obtain, are inexpensive, and have a reinforcing effect. It is preferable because it is excellent. Moreover, as a glass fiber, the average fiber diameter is about 6-20 micrometers, the average fiber length is about 1-6 mm, and the chopped strand etc. which are frequently used for the reinforcement of a phenol resin are preferable.

  The proportion of the reinforcing fibers in the total amount of the resin composition is preferably 20 to 40% by weight. If the proportion of the reinforcing fibers is less than 20% by weight, the reinforcing effect due to the addition of the reinforcing fibers, that is, the effect of improving the dimensional stability and strength of the resin pulley may not be obtained. In addition, when the proportion of the reinforcing fibers exceeds 40% by weight, there is a risk that the so-called belt attacking property, which damages a belt or the like, which is a mating member of the resin pulley, becomes strong. In addition, the ratio of the reinforcing fiber is 20 to 30% by weight in particular within the above range, considering these problems, and considering the production of a resin pulley having better characteristics. preferable.

  Examples of the inorganic filler include calcium carbonate, wollastonite, kaolinite, clay, silica, mica, alumina, zirconia, aluminum hydroxide, magnesium hydroxide, diatomaceous earth, and the like. In addition, as an inorganic filler, in consideration of improving the dispersibility with respect to the base resin and improving the fluidity of the resin composition during molding, a spherical one having an average particle diameter of 30 μm or less is used. It is preferable to use it.

  The proportion of the inorganic filler in the total amount of the resin composition is preferably 15 to 50% by weight. If the proportion of the inorganic filler is less than 15% by weight, the linear expansion coefficient of the resin pulley is reduced by adding the inorganic filler, thereby improving the dimensional stability and improving the wear resistance of the resin pulley. There is a risk that the effect will not be obtained. In addition, when the proportion of the inorganic filler exceeds 50% by weight, the proportion of the first and second novolac type phenol resins is too small depending on the proportion of the other components. It may be difficult to manufacture a resin pulley. In addition, the ratio of the inorganic filler is 25 to 45% by weight, especially within the above range, considering these problems and considering the production of a resin pulley having better characteristics. Preferably there is.

  As the lubricant, for example, a fluororesin powder excellent in lubricity, such as polytetrafluoroethylene (PTFE) powder, is preferable. The fluororesin powder as the lubricant preferably has an average particle size of 10 μm or less. Fine fluororesin powder having an average particle size of 10 μm or less can be more uniformly dispersed on the surface of the resin pulley. Therefore, it is possible to impart good slipperiness to the surface of the resin pulley only by adding a small amount of fluororesin powder. The average particle diameter of the fluororesin powder is preferably as small as possible. However, if it is too small, the dispersibility is lowered, and aggregation or the like is likely to occur, which may not be uniformly dispersed on the surface of the resin pulley. . For this reason, there is a possibility that good slipperiness cannot be given to the surface of the resin pulley. Therefore, the average particle size of the fluororesin powder is preferably 1 μm or more.

  The ratio of the lubricant such as fluororesin powder to the total amount of the resin composition is preferably 0.5 to 5% by weight. If the content of the lubricant is less than 0.5% by weight, the effect of imparting good slipperiness to the surface of the resin pulley by adding the lubricant may not be obtained. When the content of the lubricant exceeds 5% by weight, most of the lubricant is a component having lower heat resistance than the cured phenol resin such as the above-mentioned fluororesin powder. May decrease. The content ratio of the lubricant is 0.5 to 3% by weight, even in the above range, considering the production of a resin pulley having better characteristics in consideration of these problems. Is preferred.

In addition to the above components, the resin composition includes various additives such as a colorant such as a pigment and a release agent for facilitating release of the molded resin pulley from the mold. Further, it can be added within a known content ratio range.
The resin pulley of the present invention is the shape of a pulley of a mold in which the resin composition containing each component described above is heated and melted in a cylinder of an injection molding machine, and then heated in advance to a curing temperature of a phenol resin or higher. It can be manufactured by injecting into a mold cavity corresponding to the above and curing reaction of phenol resin. In addition, as described above, when the resin pulley has an insert member such as a metal, the insert member is held in the holding portion of the insert member provided in the mold cavity of the mold, and the same as described above. Thus, a resin pulley integrated with the insert member can be manufactured by injecting a phenol resin into the mold cavity to cause a curing reaction.

Example 1:
The following components were mixed using a Henschel mixer, kneaded with a hot roll heated to 85 ° C. to form a sheet, and pulverized to prepare a resin composition. A first novolac-type phenolic resin P _1, weight ratio P ₁ / P ₂ of a second novolac-type phenolic resin P ₂ was a _{P 1 / P 2 = 55/} 45. The total amount of both novolak-type phenol resins was 30 parts by weight.

(Ingredients) (Parts by weight)
1st novolac type phenolic resin P ₁ 16.5
(Number average molecular weight Mn ₁ = 800)
Second novolac type phenolic resin P ₂ 13.5
(Number average molecular weight Mn ₂ = 1100)
・ Spherical silica powder 39
(Average particle size 20 μm)
・ Glass fiber 20
(Average fiber diameter 13 μm, average fiber length 250 μm)
・ Fluororesin powder 2
[Lubron (registered trademark) L-2 manufactured by Daikin Industries, Ltd., average particle size: 10 μm]
・ Hexamethylenetetramine 4
・ Pigments, release agents, etc. 5
In addition, the number average molecular weights of the first and second novolak type phenol resins were measured using a high performance liquid chromatograph [HLC-802A manufactured by Tosoh Corporation] as a column and a TSK-Gel column G3000H8 manufactured by Tosoh Corporation (× 1), G2000H8 (× 2) and G1000H8 (× 1) were loaded and measured.

  Next, the resin pulley 1 shown in FIG. 1 has a mold cavity corresponding to the shape of the pulley body 11, and the outer ring 21 of the ball bearing 2 is located at a position corresponding to the center of the pulley body 11 of the mold cavity. Prepare a film gate mold with a holding part to hold the mold, set the mold in an injection molding machine and heat it to 170 ° C, and supply the above resin composition to the hopper of the injection molding machine did.

The resin composition softened in the cylinder with the ball bearing 2 including the outer ring 21, the ball 22, the inner ring 23, the cage 24, and the seals 25, 26 set in the mold holding part and clamped Was injected into the mold cavity, filled and cured, and the pulley body 11 was molded to produce the resin pulley 1.
Examples 2-5:
The weight ratio P ₁ / P ₂ between the first novolac type phenolic resin P ₁ and the second novolac type phenolic resin P ₂ is P ₁ / P ₂ = 35/65 (Example 2), P ₁ / P Example 1 except that ₂ = 45/55 (Example 3), P ₁ / P ₂ = 65/35 (Example 4), and P ₁ / P ₂ = 75/25 (Example 5) Similarly, a resin pulley was manufactured. In all examples, the total amount of both novolak type phenol resins was 30 parts by weight as described above.

Comparative Example 1:
In the same manner as in Example 1, except that 30 parts by weight of one kind of novolac type phenol resin having a number average molecular weight Mn of 500 was used instead of the first and second kinds of novolak type phenol resins, A resin pulley was manufactured.
Comparative Example 2:
Instead of the first and second two types of novolac type phenol resins, the same procedure as in Example 1 was conducted except that 30 parts by weight of one type of novolac type phenol resin having a number average molecular weight Mn of 800 was used. A resin pulley was manufactured.

Comparative Example 3:
In the same manner as in Example 1, except that 30 parts by weight of one kind of novolac type phenol resin having a number average molecular weight Mn of 1000 was used instead of the first and second kinds of novolak type phenol resins, A resin pulley was manufactured.
Comparative Example 4:
In the same manner as in Example 1, except that 30 parts by weight of one kind of novolak type phenol resin having a number average molecular weight Mn of 1100 was used instead of the first and second kinds of novolak type phenol resins. A resin pulley was manufactured.

Thermal shock resistance test:
The resin pulley 1 manufactured in the example and the comparative example was cooled at −40 ° C. for 30 minutes and then heated at 120 ° C. for 30 minutes, and the cycle was repeated 2000 times. It was observed whether cracks occurred. And those with no cracks at all were excellent in thermal shock resistance (◎), those with slight cracks, but those that did not interfere with practical use were good with thermal shock resistance (◯), and those with many cracks The thermal shock resistance was evaluated as poor (x).

Formability test:
In Examples and Comparative Examples, it was observed whether or not molding failure such as filling failure or gas burn occurred in the pulley body 11 immediately after molding. In addition, those in which these molding defects did not occur at all were excellent in moldability (◎), and although molding defects were slightly seen, those that were not practically inferior in good moldability (◯), due to molding defects Those that could not be used were evaluated as poor moldability (x).

  The results are shown in Table 1.

From the table, it was found that the pulleys 1 of Comparative Examples 1 and 2 manufactured by using a novolak type phenol resin having a small number average molecular weight Mn alone had poor thermal shock resistance and cracks were generated in the pulley body 11. . Further, the pulley 1 of Comparative Examples 3 and 4 manufactured by using a novolak type phenol resin having a large number average molecular weight Mn alone has poor moldability, and the pulley 1 has molding defects such as poor filling and gas burn. It occurred and was found to be unusable. On the other hand, Examples 1 to 5 produced by using a first novolac type phenol resin having a number average molecular weight Mn ₁ of 800 and a second novolac type phenol resin having a number average molecular weight Mn ₂ exceeding 1100 in combination. Each of the pulleys 1 was found to have good thermal shock resistance and moldability (◯) or very good (◎). Furthermore, when comparing the examples, the two phenolic novolak resin, was also found that preferably blended in a range of weight ratio _{P 1 / P 2 = 40 /} 60~70 / 30.

It is sectional drawing which shows an example of the resin pulleys manufactured in the Example of this invention.

Explanation of symbols

1 Resin pulley 11 Pulley body

Claims (4)

A resin pulley comprising a resin composition containing a phenol resin as a base resin, wherein the phenol resin is a first novolac type phenol resin having a number average molecular weight Mn ₁ of 850 or less, and a number average molecular weight Mn ₂ of 850. A resin pulley characterized by using a second novolac-type phenolic resin in combination. The resin pulley according to claim _1, wherein the number average molecular weight Mn _{1 of} the first novolac type phenolic resin is 750 to 850. 2. The resin pulley according to claim 1, wherein the number average molecular weight Mn _{2 of} the second novolac type phenol resin is 1050 to 1150. 3. Number first novolak type phenolic resin P ₁ average molecular weight Mn ₁ is 750 to 850, a number average molecular weight Mn ₂ is a second novolak type phenolic resin P ₂ is from 1050 to 1150, the weight ratio P ₁ / The resin pulley according to claim 1, which is used at a ratio of P ₂ = 40/60 to 70/30.

Images