JP2588891B2 - Polyolefin-based composition for sliding material - Google Patents

Description

The present invention relates to a composition for a polyolefin-based sliding material.

[Conventional technology]

Polyolefins such as polyethylene and polypropylene have many excellent chemical and physical properties, have a low coefficient of friction, but have relatively high abrasion, especially under high load (surface pressure P) or high speed (speed V) conditions. In other words, it cannot be used at all under sliding conditions with a large PV value, and because of its high coefficient of thermal expansion, it cannot be used in fields requiring high dimensional accuracy with respect to temperature changes. Has considerable limitations. Therefore, attempts have been made to improve the abrasion properties by blending various lubricating substances such as polytetrafluoroethylene resin, graphite, lubricating oil, etc. with polyolefin, but it has been attempted to improve the abrasion resistance with low friction. No material has been developed yet that has excellent wear resistance even when the PV value is high.In terms of coefficient of thermal expansion, the addition of these lubricating substances does not improve the effect. In most cases, it is not recognized or worsens. Attempts have also been made to improve the mechanical strength and heat resistance of the polyolefin by cross-linking, and although the abrasion resistance or the coefficient of thermal expansion is somewhat improved, the coefficient of friction is still large and satisfactory. Not. Furthermore, ultra-high molecular weight polyethylene has been developed as a polyolefin having relatively excellent wear resistance and coefficient of friction, but it is difficult to mold because it has a high viscosity when melted and cannot be easily injection molded. Yes, economic disadvantages are inevitable, and little improvement has been made in terms of the coefficient of thermal expansion. Also, in order to improve the moldability of such ultra-high molecular weight polyethylene, a method of setting the average molecular weight within the ultra-high molecular weight region and widening the molecular weight distribution has been proposed, but such means have a friction coefficient. It is only effective for improving either one of the wear resistance and the wear resistance, and the effect on the wear resistance and the coefficient of thermal expansion under the condition of a high PV value can hardly be expected. Incorporating a fibrous filler for the purpose of further reducing the coefficient of thermal expansion is a technique that has already been widely used for other thermoplastic resins, but the wettability of polyolefin is poor. , A good adhesive strength with the filler is not obtained, the coefficient of thermal expansion is not improved, but rather the lubricating property is deteriorated, and a bad effect occurs when the surface of the sliding partner material is damaged, which is preferable. Absent. On the other hand, the most common sliding material using a synthetic resin other than polyolefin is a tetrafluoroethylene resin containing a filler, but this resin is also poor in moldability and is expensive, There is a strong demand for the development of a material having the same sliding characteristics, good moldability, and low cost.

[Problems to be solved by the invention]

As described above, in the prior art, polyolefins having many excellent properties such as chemical properties, physical properties, and moldability also have a low friction coefficient, abrasion resistance, a high critical PV value, and a small coefficient of thermal expansion. There is a problem that it is not compatible with the required sliding material.

[Means for solving the problem]

In order to solve the above problems, the present invention provides a modified olefin resin 10 obtained by graft-polymerizing an unsaturated silane compound.
Based on 0 parts by weight, a thermosetting resin has 15 to 65 parts by weight, and further has a unit containing a polar group with -C _X F _2X -O- (where x is an integer of 1 to 4) as a main structural unit. 1 to 20 parts by weight of a fluoropolymer composed of polyfluoroether was blended, and this was exposed to an atmosphere of water in the presence of a silanol condensation catalyst to form a crosslinked polyolefin-based sliding material composition. Things. The details are described below.

First, in the present invention, the modified olefin resin obtained by graft-polymerizing an unsaturated silane compound is, for example, a trade name of "Linklon" or "Linklon-" manufactured by Mitsubishi Yuka.
X "or" Linklon-PP "such as organosilane-modified high- or low-density polyolefin such as polyethylene or polypropylene, and the active silane group (-Si-OR, where R is an alkyl group) of the entire polyolefin. ) Is usually
It is less than 10%. Such an active silane group is crosslinked in the presence of water, and a catalyst (for example, dibutyltin dilaurate) may be appropriately added in order to smoothly promote the crosslinking reaction with water. A method for producing such a modified polyolefin is disclosed, for example, in Japanese Patent Publication No. 48-1711.

Next, the thermosetting resin of the present invention has an affinity, preferably a hydroxyl group, a carboxyl group, a methylol group, an amino group, having an affinity for a polar group of a fluorine-containing polymer described later.
Those containing at least one of the epoxy groups are desirable, and phenol resins and epoxy resins are particularly preferable from the viewpoint of thermal stability during melt blending. Examples of the phenol resin include a phenol-alkyl resin and a phenol-formaldehyde resin. That is, the phenol-alkyl resin is And a commercially available product such as “Mirex XL-225” (trade name, manufactured by Mitsui Toatsu Chemicals Co., Ltd.). The phenol-formaldehyde resin is, for example, a phenol-aldehyde resin which is a condensate of a phenol and an aldehyde, or a nitrogen-containing phenol-aldehyde copolymer resin which is a condensate of a phenol, a nitrogen-containing compound and an aldehyde. is there. Here, phenols include phenol, cresol, xylenol, alkylphenol, resorcinol, etc., aldehydes include formalin, paraformaldehyde, trioxane, etc., and nitrogen-containing compounds include at least urea, aniline, melamine, guanidine, etc. Compounds having two active hydrogens can be exemplified. Numerous processes for producing such phenolic resins are already known, for example, from JP-A-57-17701, JP-A-58-17114 and others. And the like. And, as mentioned above,
It is desirable that such a thermosetting resin has an active group that is new or reactive to the polar group of the fluorine-containing polymer. Therefore, in the case of a phenol resin, the methylol index is 0.2. It is preferable that it is above. Here, the methylol index is a numerical value capable of estimating the reactivity in the phenol resin, that is, the amount of free methylol groups, and is one of the values obtained by infrared absorption spectrum analysis using the KBr tablet method.
For absorption intensity of the characteristic absorption of the benzene nucleus in 600 cm ^-1 (this product is referred to as D _B), the greatest absorption intensity of the characteristic absorption of the methylol groups in 990~1020cm ^-1 (this
Represented by the ratio D _M / D _B of D _M abbreviated). A larger value indicates that there are more free methylol groups, which means that the reactivity is richer.However, if this value is too large, that is, if the amount of free methylol groups is too large, the reactivity becomes excessive, Upon mixing with the modified polyolefin, the composition cures in a very short time, resulting in poor uniform dispersibility upon melting, making it impossible to obtain a homogeneous composition. Therefore, the methylol index is preferably 0.
2 to 6.0. In addition, those which do not cause a curing reaction unless a crosslinking agent such as hexamethylenetetramine is added,
It is desirable to add it for forming a three-dimensional network structure of a resin which is extremely effective in improving abrasion resistance and coefficient of thermal expansion at a high PV value. As the epoxy resin, a liquid or solid epoxy resin containing two or more epoxy groups at room temperature can be used. Specifically, bisphenol-based, alicyclic, novolak-type or other epoxy resins can be used more effectively. For this purpose, it is preferable to use a curing agent such as an amine, an acid anhydride, a polysulfide, or a phenol resin in addition to the epoxy resin main agent.

The addition amount of the above thermosetting resin was
The reason for setting the amount to 15 to 65 parts by weight with respect to 0 part by weight is that a small amount of less than 15 parts by weight reacts with the thermosetting resin itself or a polar group of a fluorine-containing polymer described later to form a three-dimensional network structure. As a result, the degree of entanglement with the network of the modified olefin resin is too small even if it is not formed or formed,
This is because the abrasion resistance at a high PV value is inferior, and the coefficient of thermal expansion is large. Conversely, a large amount exceeding 65 parts by weight adversely affects lubricity.

Further, the polyfluoroether as a fluorine-containing polymer in the present invention is a polymer having an average molecular weight of 1,000 to 50,000, having -C _X F _2X -O- (where x is an integer of 1 to 4) as a main structural unit. It is. And the fluorine-containing polymer made of this polyfluoroether has a polar group such as an epoxy group, an amino group,
It has a unit containing a hydroxyl group, a carboxyl group, a mercapto group, an isocyanate group and the like, and specific examples include the following. _{That, OCN-C 6 H 3 (} CH 3) -HNCOCF 2 C 2 F 4 O m CF 2 O n CF 2 CO
_{NH- (CH 3) C 6 H} 3 -NCO, HOOC-CF 2 OC 2 F 4 O m CF 2 O n CF 2 COOH, H ₃ COOC-CF ₂ OC ₂ F ₄ O _m CF ₂ O _n CF ₂ COOCH ₃ , HOCH ₂ -CF ₂ OC ₂ F ₄ O _m CF ₂ O _n CF ₂ -CH ₂ OH, HOCH _{2 2} NHCO-CF ₂ OC ₂ F ₄ O _m CF ₂ O _n CF ₂ CONHC
H _{2 2} OH, H ₂ NCH _{2 2} NHCO-CF ₂ OC ₂ F ₄ O _m CF ₂ O _n CF ₂ CONH
CH _{2 2} NH ₂ , N≡CO—C ₆ H ₃ (CH ₃ ) = HNCOCF ₂ C ₂ F ₄ O _m CF _{2
n CF 2 CONH-C 6 H} 3 (CH 3) -O-C≡N , and the like.

When the above-mentioned fluorine-containing polymer having a unit containing a polar group is combined with an active functional group of a thermosetting resin so as to partially or substantially react with each other, the fluorine-containing polymer is included by the reaction. Because the fluoropolymer is firmly held in the network structure of the thermosetting resin, it is difficult to be detached even when subjected to external stimuli such as stress such as shearing force or compressive force or heat. As a result, exercise within the
It is effective in reducing the abrasion resistance or the coefficient of thermal expansion under the PV value. For example, when the thermosetting resin contains a hydroxyl group, an amino group, or a methylol group, a polymer containing an epoxy group, an isocyanate group, or a carboxyl group is used as a fluorine-containing polymer. When the thermosetting resin contains a carboxyl group, an amino group, a hydroxyl group, or an isocyanate is used as a fluorine-containing polymer when the thermosetting resin contains a carboxyl group. When the fluorine-containing polymer containing a group is a thermosetting resin further containing an isocyanate group, it may be combined with a fluorine-containing polymer containing a hydroxyl group, an amino group, a mercapto group, a carboxyl group, an ester group, or the like. desirable. It is important that the fluorine-containing polymer is firmly held by the thermosetting resin. For this reason, it is preferable that the fluorine-containing polymer has polar groups at both ends. This is because the fluorine-containing polymer forms part of the skeleton of the three-dimensional network of the thermosetting resin together with the effect of increasing the number of reaction points (for one terminal), and the modified olefin having a partially crosslinked structure This is because, as a result of being entangled with the resin network structure and reinforcing each other, a more stable material structure is formed, which contributes to a reduction in wear resistance and a coefficient of thermal expansion.

The amount of the fluorine-containing polymer is
The reason for using 1 to 20 parts by weight with respect to 100 parts by weight is that if the amount is less than 1 part by weight, the effect of improving the sliding characteristics, particularly lubricity, is insufficient, and if the amount exceeds 20 parts by weight, the modification is This is because the mechanical strength of the olefin resin is significantly reduced.

In order to mix various raw materials such as the modified olefin resin, the thermosetting resin, and the fluorine-containing polymer, a conventionally well-known method may be used. For example, the modified olefin resin and other compounding components may be used. Individually or, for example, appropriately dissolved in a solvent such as fluorochlorohydrocarbon, and mixed by a mixer such as a Hensiel mixer, a ball mill, and a tumbler mixer, and then the solvent is removed.
It may be supplied to an injection molding machine or a melt extruder having good melt-mixing properties, or may be melt-mixed in advance using a hot roller, a kneader, a Banbury mixer, a melt extruder, or the like.
The method of molding the composition of the present invention is not particularly limited, but compression molding, extrusion molding, injection molding, and the like are practical, and the composition of the present invention is melt-mixed. After that, the powder is pulverized by a jet mill, a freezing pulverizer or the like, and the powder as it is or classified into a desired particle size can be used as a powder coating for fluid immersion coating, electrostatic powder coating and the like. Particularly when high fluidity is required during molding, a masterbatch (base is polyolefin) containing about 1% of a catalyst (for example, dibutyltin dilaurate) which promotes crosslinking by water is melt-mixed with the composition of the present invention. After that, a method of dry blending and subjecting to various melt molding may be adopted. In the composition of the present invention, various additives usually used may be appropriately used in a range not impairing the object of the present invention, and may be added and compounded simultaneously with the above-mentioned compounding agents. Can also be adopted.

Such additives are, for example, release agents, flame retardants, weather resistance improvers and the like, and it is of course possible to use conventional and publicly known lubricants together, and it is also possible to use tetrafluoroethylene resin powder, graphite, Graphite fluoride, talc, boron nitride, and other industrial lubricants can also be appropriately selected and used according to the purpose of use. In addition, known fibrous substances such as glass fiber, carbon fiber, alumina fiber, asbestos, rock wool, wollastonite, potassium titanate whisker, or inorganic substances represented by glass powder, talc, clay, calcium carbonate, etc. Fillers and the like can also be used. In any case, as long as the lubricating and abrasion resistance and the low coefficient of thermal expansion of the composition of the present invention are not impaired, modification to improve properties by chemical or physical treatment in the form of an intermediate product or final product is required. Of course, it is possible.

Finally, the exposure to the atmosphere of water in the present invention is carried out by molding the composition into a desired shape, and then, after molding the molded product from room temperature to 200 ° C.
About, usually liquid or gaseous water at room temperature to about 100 ° C for about 10 seconds to about 1 week, usually about 1 minute to 1 day,
The contact is preferably carried out for a long time, whereby the crosslinking reaction of the composition is almost complete.

[Action]

The three-dimensional network structure formed by the reaction between the functional group of the thermosetting resin itself or the functional group of the thermosetting resin and the polar group of the fluorine-containing polymer forms a network structure by crosslinking of the modified olefin resin itself with the graft-polymerized silane group. The different meshes reinforce each other to provide excellent abrasion resistance, especially at high PV values, not only to reduce the coefficient of thermal expansion but also to provide excellent lubricity. The polar group of the coalescence shows a large affinity or a strong bonding force with the thermosetting resin, and because it exists finely dispersed, the coefficient of friction is small, and it remains in the tissue without falling off from the base material. It is considered that the friction coefficient is stably maintained.

〔Example〕

First, raw materials used in the following examples and comparative examples are collectively shown as follows. In addition, abbreviations are shown in [] and all the mixing ratios are expressed in parts by weight.

(1) Polyolefin resin [PO] Modified polyethylene (Mitsubishi Yuka Co., Ltd .: Linklon HF700)
N) [PO-1], modified polypropylene (manufactured by Dojo Co., Ltd .: Linklon XPM800)
H) [PO-2] High-density polyethylene (manufactured by Mitsui Petrochemicals: Hijets J1300) [PO-3], polypropylene (manufactured by Mitsui Petrochemical: Polypro J600) [PO-
4), ultra-high molecular weight polyethylene (Hijets Million 240M, manufactured by Dojo Co., Ltd.) [PO-5], (2) Silanol condensation catalyst [Catalyst] A master batch containing a silanol condensation catalyst for the above [PO-1] (Mitsubishi Yuka Manufactured by Lincoln HZ051) [catalyst-1], master batch containing silanol condensation catalyst for the above [PO-2] (manufactured by Rintron PZ010S) [catalyst-
2], (3) Fluorinated polymer [FC-1-4, FC-7] and fluorinated compound [FC-5, FC-6] hydroxyl-containing polyfluoroether (average molecular weight of about 200
0) [FC-1] _{HOCH 2 -CF 2 HC 2 F 4} O m CF 2 O n CF 2 -CH 2 OH, an isocyanate group-containing polyfluoroether (average molecular weight of about 2000) [FC-2] OCN-C _{6 H 3 (CH 3) -NHCOCF 2} C 2 F 4 O m CF 2 O n CF 2 CO
_{NH-C 6 H 3 (CH} 3) -NCO, carboxyl group-containing polyfluoroether (average molecular weight of about 2000) [FC-3] _{HOOC-CF 2 OC 2 F 4} O m CF 2 O n CF 2 -COOH, carboxyl Group-containing polyfluoroether (average molecular weight about 1500) [FC-4] Epoxy group-containing polyfluoroalkyl (average molecular weight about
570) [FC-5] Amino group-containing polyfluoroalkyl (average molecular weight of about 51
0) [FC-6] C ₆ F ₁₃ SCH ₂ CH ₂ OCO (CH ₂ ) ₅ —NH ₂ , (inert) polyfluoroether (average molecular weight about 15
000) [FC-7] _{F 3 C-CF 2 OC 2} F 4 O m CF 2 O n CF 2 -CF 3, (4) an organopolysiloxane [OPS] hydroxyl group-containing organopolysiloxane (Shin-Etsu Chemical Co., Ltd. Silicone diol X-22-160C) [OPS-1], epoxy-containing organopolysiloxane (manufactured by Dojo Corporation: Epoxy-modified silicone oil KF102) [OPS-2], (5) Tetrafluoroethylene resin polytetrafluoroethylene (Mitsui DuPont Fluorochemical Co., Ltd .: TLP-10) [PTFE], (6) Thermosetting resin, phenol / alkyl resin (Mitsui Toatsu Chemicals: MILEX XL-225) [PH-1], phenol / formaldehyde resin (Kanebo: Bellpearl S970, methylol index 0.3) [PH-2], phenol / formaldehyde resin (manufactured by Kamibo: Bellpearl R900, methylol index 0.4) [PH-3], bisphenol A type Epoxy resin (base) (Mitsubishi Petrochemical: EPOMIK-R-140) [EP-1], Novolatck type epoxy resin (base) (Ciba Geigy: Araldite ECN-1280) [EP-2], (7) Curing agent Hexamine (curing agent for the above-mentioned [PH-1]) [Curing agent-1], Epoxy resin curing agent (Mitsui Petrochemical Co., Ltd .: Novolac type phenolic resin High Polyk 2000) [Curing agent-2], Epoxy resin curing (Novolak type phenolic resin BRG-557 [hardener-3], manufactured by Showa Union Gosei Co., Ltd.).

Examples 1 to 7, Reference Examples 1 to 3: Raw materials were dry-mixed with a Hensiel mixer at the mixing ratios shown in Table 1 and then supplied to a kneader, kneaded at 180 ° C and 65 rpm, and crushed. I got a pellet. This pellet was injection molded under the conditions of a resin temperature of 190 ° C, an injection pressure of 800 kg / cm ² , and a mold temperature of 50 ° C. A cylindrical test piece having an outer diameter of 23 mm, an inner diameter of 14 mm, and a length of 13 mm, an ASTM-D638 IV dumbbell Test piece and outer diameter
A columnar test piece having a length of 8 mm and a length of 10 mm was obtained. After immersing each of the obtained test pieces in hot water at 80 ° C. for 24 hours, the tensile strength, the coefficient of friction, the coefficient of wear and the coefficient of thermal expansion were evaluated, and the results are summarized in Table 2. In addition, the evaluation method of these various properties is as follows.

1) Tensile strength (kg / cm ² ) Conforms to ASTM-D634 using IV type dumbbell specimens.

2) Coefficient of friction A thrust-type friction and wear tester was used for the cylindrical test piece, and the sliding speed was 1 minute per minute against the bearing steel (SUJ-2).
A friction test is performed under the conditions of m and a load of 10 kg / cm ² , and a friction coefficient one hour after sliding is determined.

3) Wear coefficient A wear test is performed under the following three conditions using the same test piece, test machine, and mating material as those for which the friction coefficient is obtained, and the weight is calculated from the weight change before and after the test.

a) Load P = 3.125 kg / cm ² , sliding speed V = 32 m / min, ie, PV = 100 b) Load P = 1.563 kg / cm ² , sliding speed V = 128 m / min, ie, PV = 200 c) Load P = 3.125 kg / cm ² , sliding velocity V = 128 m / min, ie, PV = 400 4) Thermal expansion coefficient Based on the TMA method using a thermomechanical analyzer manufactured by Shimadzu Corporation for the cylindrical test piece, 0 Determine the coefficient of thermal expansion in the range of 8080 ° C.

Comparative Examples 1 to 13: Various raw materials were mixed at the mixing ratios shown in Tables 3 and 4. Except for Comparative Example 12, the same operation as in Example 1 was carried out to produce various test pieces. 210 for Comparative Example 12
It was compression molded under the conditions of ° C and a pressure of 100 kg / cm ² to prepare a test piece. Various characteristics were evaluated for each of these test pieces in the same manner as in Example 1, and the obtained results are summarized in Table 5.

The following is clear from Tables 2 and 5.
That is, Examples 1 to 7 hardly reduce the tensile strength, have a small coefficient of friction, are excellent in wear resistance, and particularly maintain a good value of the coefficient of wear of a high PV value.
Since the purpose of low friction and low abrasion is achieved without adding a hard filler, there is no damage to a sliding partner material in sliding. Also, the coefficient of thermal expansion has a small value. On the other hand, Comparative Example 2 containing no thermosetting resin, Comparative Example 5 containing too much fluorine-containing compound,
Comparative Example 6 in which the fluorine-containing polymer does not have a polar group, Comparative Examples 7 and 8, in which the lubricant is an organopolysiloxane,
Comparative Examples 9 and 10 in which the polyolefin is other than the present invention, and Comparative Example 11 in which the lubricant is tetrafluoroethylene resin
And Comparative Example 12, in which the polyolefin is other than that of the present invention and the lubricant is a tetrafluoroethylene resin, has good lubricating properties, but all have abrasion resistance at a high PV value. The thermal expansion coefficients except for Comparative Examples 7 and 8 are also large. Comparative Example 1 containing only modified olefin,
Comparative Example 3 in which the amount of the thermosetting resin added was too large, Comparative Example 4 in which the fluorine-containing polymer was not contained, and Comparative Example 13 in which the polyolefin was an ultrahigh molecular weight polyethylene had a large coefficient of friction and poor lubricity. Other than the above, the wear resistance at a high PV value and the coefficient of thermal expansion were unsatisfactory values. On the other hand, Examples 1 to
No. 7 has good properties in all respects, and has an equivalent or smaller coefficient of thermal expansion than Comparative Examples 1 and 4 in which a lubricating component was introduced but no lubricating component was introduced. What I showed was surprising.

Furthermore, comparing Reference Example 2 and Reference Example 3, it is found that the phenol resin (main agent) commonly used for both is a type of resin that requires a curing agent to form a three-dimensional network, but a curing agent is used. It can be seen that Reference Example 3 was superior to Example 4 in which no abrasion resistance and thermal expansion coefficient were obtained under a high PV value. When Examples 3 and 4 are compared, Example 3 in which the polar group of the fluoropolymer is present at both terminals has a smaller coefficient of friction and a smaller coefficient of thermal expansion than Example 4 which is a single terminal. You can see that there is.

〔effect〕

A molded article comprising the polyolefin-based sliding material composition of the present invention retains the original mechanical strength of polyolefin,
In addition to having excellent lubrication properties and wear resistance,
By exhibiting good abrasion resistance against sliding under high loads and high speeds, which were the weak points of conventional polyolefins, it greatly expanded the use conditions that had been restricted so far,
Another disadvantage is that the size of the coefficient of thermal expansion has also been improved, so that it can be used in the field of precision equipment that requires small dimensional accuracy with respect to temperature changes, and can be used in a wide range of fields. Since it is optimal as a moving material, it can be said that the significance of the present invention is extremely large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F16C 33/20 7123-3J F16C 33/20 A

Claims (2)

(57) [Claims] 1. A thermosetting resin is added to 100 parts by weight of a modified olefin resin obtained by graft polymerization of an unsaturated silane compound.
To 65 parts by weight, and furthermore, -C _X F _2X -O- (where x is an integer of 1 to 4), as a main structural unit, and a fluoropolymer 1 comprising a polyfluoroether having a unit containing a polar group. A composition for a polyolefin-based sliding material, comprising 20 parts by weight, and exposing the composition to a water atmosphere in the presence of a silanol condensation catalyst to cause crosslinking. 2. The polyolefin-based slide according to claim 1, wherein the thermosetting resin is a thermosetting resin containing at least one of a hydroxyl group, a carboxyl group, a methylol group, an amino group, and an epoxy group. Composition for moving material.