JP2001131569A - Solid lubricant for food equipment and rolling bearing for food equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid lubricant for food equipment free from wash away by water, capable of enduring continuous use at >150 deg.C, and a rolling bearing for food equipment hard to rust on the sliding face in a condition in contact with saline water by sealing a bearing with the lubricant. SOLUTION: This solid lubricant for food equipment is obtained by mixing 5-95 wt.% of a lubricant comprising one or more kind of oils selected from an ester oil, a silicone oil and a polyalkylene glycol oil or a grease utilizing the lubricant as the base oil and 95-5 wt.% of a polyamide powder or a polyacetal powder and heat molding at a temperature higher than a gel point of the powdered resin. And a bearing for food equipment comprising a stainless steel rolling bearing sealed inside with the prescribed solid lubricant for food equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubricant for food machinery and a rolling bearing for food machinery in which the solid lubricant is encapsulated.

[0002]

2. Description of the Related Art Food machinery sorts, cuts, and sorts food materials.
Grinding, heat treatment, concentration, filtration, separation, mixing, kneading, heating,
Machines used for drying, cooling, filling, molding, packaging, storage, preservation, etc., which come into direct or indirect contact with food raw materials and products (or semi-finished products), especially water and salt. It is a lot of machinery.

[0003] In such food machines, bearings and other sliding parts are mounted on parts that rotate and slide similarly to other machinery, but lubricants and other chemical substances are mounted on the sliding parts. It may be applied, filled, mixed, etc. In food machines, it is necessary to prevent toxic components from leaking out of the sliding parts into the human body and mix into the food.Therefore, components of lubricants that can be used in accordance with the sanitary standards stipulated by law are used. Stipulated.

[0004] As sanitary standards for lubricating greases, FDA (US Food and Drug) or USDA (US Department of Agriculture and Commerce) approval standards are well known, and grease for food machinery is known separately from general industrial grease. Have been.
Incidentally, USDA category H1 (abbreviated as USDA H1) is defined by the FDA (US Food and Drug Administration).
o. Lubricants made with human-safe base oils and additives that meet the requirements of 21 CFR 178.3570, which the USDA has declared "Use in food machinery where food and lubricating oils may come into inadvertent contact. It is a safe lubricating oil that can be used. "

By the way, the inventors of the present application have reported that ultra-high molecular weight polyethylene is used as a solid lubricant for general industrial use.
Lubricating grease having a drop point higher than the melting temperature of the polyethylene is blended, and heated to a temperature higher than the melting temperature to fill the bearing and solidify the lubricant.
No. 239. Such a solid lubricant is a solid lubricant in which a lubricating component hardly flows out of the bearing, which is also referred to as a plastic grease.

Further, US Pat. No. 3,547,819 discloses that a solid lubricant is made of a hydrocarbon oil having lubricity as a lubricating component and mixed with ultra high molecular weight polyethylene having an average molecular weight of 1.5 × 10 ^{6 to} 5 × 10 ^6. A solidified lubricating composition for bearings is disclosed.

[0007]

However, the above-mentioned conventional solid lubricants for bearings do not always contain lubricating components satisfying the hygiene standards applicable to food machines. Only the specified rust inhibitor confirmed to be able to be added can be used, so that the solid lubricant that can be used as a solid lubricant for food machinery and the rolling bearing for food machinery that encapsulates it has satisfactory rust prevention and lubricity. There was nothing to do.

Further, the above-mentioned conventional solid lubricants for food machinery are not satisfactory in terms of heat resistance, and are not suitable for the melting point of ultra high molecular weight polyolefin (for example, 136 ° C.) or the melting point of high density polyethylene. It could not be used at a temperature of 120 ° C. or higher, and in particular, none had heat resistance that could be used continuously at a high temperature of 120 ° C. or higher.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a solid food machine solid lubricant,
Durable under high temperature conditions in contact with water, especially 12
An object of the present invention is to provide a solid lubricant for food machinery that does not deform when continuously used at 0 ° C. or higher and does not easily generate rust on a sliding surface made of steel even under conditions of being in contact with a salt solution and has excellent rust prevention.

A water-resistant rolling bearing filled with a solid lubricant which can be used continuously at a high temperature of 120 ° C. or higher,
An object of the present invention is to provide a rolling bearing for food machinery that does not easily generate rust on a sliding surface made of steel even under use conditions such as contact with water containing salt.

[0011]

According to the present invention, there is provided a lubricating oil containing at least one oil selected from an ester oil, a silicone oil and a polyalkylene glycol oil. 5 to 95% by weight of grease to be oil and 95 to 5% by weight of polyamide powder
Was heated to a temperature equal to or higher than the gel point of the polyamide powder to form a solid lubricant for food machinery.

In the above solid lubricant for food machinery, the above-mentioned problem can be solved even with a solid lubricant for food machinery using polyacetal powder instead of polyamide powder.

[0013] Further, the above problem has been solved by providing a rolling bearing for food machinery in which the above-mentioned solid lubricant for food machinery is sealed inside a rolling bearing made of stainless steel.

The oil used for the solid lubricant for food machinery of the present invention is selected from ester oils, silicone oils and polyalkylene glycol oils, and if these are less than a predetermined concentration, they do not cause harm to the human body. As USD
It has passed the AH-1 standard (evaluation standard that it is harmless to humans even if it comes into direct contact with food) or the FDA standard. Polyamides and polyacetals are substances that have been confirmed to be safe even if they come into contact with foods by the Food Sanitation Law (Ministry of Health and Welfare) or FDA standards.

The polyamide used in the present invention (melting point: 179 to 265 ° C., linear expansion coefficient: 8 to 10 × 10 ⁻⁵ cm)
/ Cm / ° C), polyacetal (melting point 175-181)
° C, coefficient of linear expansion 8.5 to 10 × 10 ^-5 cm / cm / ° C)
Is a material that can be used as a solid lubricant without deformation even at 150 ° C., because its melting point is higher than the melting point of ultrahigh molecular weight polyolefin and its linear expansion coefficient is small.

The solid lubricant for food machinery of the present invention is a solid lubricant in which a resin having the required physical properties such as the above-mentioned polyamide and polyacetal is employed and a lubricating oil harmless to food hygiene is dispersed and held therein. Therefore, it does not flow out due to water or the like that has entered the inside of the bearing, and has heat resistance that allows continuous use even at a high temperature of 150 ° C.

The solid lubricant for food machinery of the present invention maintains the lubricating properties for a long period of time by leaching lubricating oil or grease base oil at an appropriate speed, and is filled and sealed inside the rolling bearing. When used, the lubricating oil forms a rust-preventive film on the inner and outer ring rolling surfaces, rolling elements or the inside of the bearing, such as a steel plate retainer. It becomes a rolling bearing that can be used.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The ester oil used in the present invention is:
A well-known ester oil having a -COO- structure such as a dibasic acid ester, a polyol ester, a phosphate ester, and a silicate ester, wherein the above-mentioned FDA (US Food and Drug Administration) is an indirect food additive. Is a synthetic lubricating oil consisting of the compounds specified in (1). Specific examples of ester oils specified by the FDA include monohydrogen phosphate esters, dihydrogen phosphate esters, and the like.

The silicone oil used in the present invention is a silicone oil known as a polymer type synthetic lubricating oil and designated by the aforementioned FDA. The silicone oil represented by the following chemical formula 1 (for example, dimethylpolysiloxane) Siloxane).

[0020]

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(In the formula, R is a simple or mixed group of a methyl group and a phenyl group.) Specific examples of such a silicone oil (organopolysiloxane) include alkylmethyl silicone such as dimethyl silicone and phenyl Methyl silicone and the like can be mentioned.

The polyalkylene glycol oil used in the present invention is polyethylene glycol, polypropylene glycol, etc., which are well known as synthetic lubricating oils, and these are synthetic lubricating oils specified by the aforementioned FDA.

In the present invention, of the lubricating oils described above,
A lubricating oil containing one or more oils can be used.

The grease of the present invention is a grease based on a lubricating oil containing one or more oils selected from ester oils, silicone oils and polyalkylene glycol oils. Aluminum composite soap, calcium hydrostearate,
Polyurea, clay, fluororesin, etc. are blended and thickened.

The polyamide powder used in the present invention comprises an amide group (-CONH) between aliphatic and aromatic carbon molecular chains.
This is a powder of a thermoplastic synthetic resin having-), and a resin having a polyamide group can be employed without particular limitation as a material of the powder. The melting point of such a polyamide is 179
２６265 ° C., coefficient of linear expansion 8 × 10 ^-5 to 10 × 10 ^-5 cm
/ Cm / ° C.

Specific examples of polyamides (common names are shown in parentheses) include polyamide 11 (11 nylon), polyamide 12 (12 nylon), and polyamide 46 (46 nylon).
Nylon), polyamide 6 (nylon 6), polyamide 6-6 (66 nylon), polyamide 6-66 (6/6
6 nylon), polyamide 6-10 (610 nylon), polyamide 6-12 (6/12 nylon), polyamide 12-12 (1212 nylon), polyamide M
XD6 (MXD-6 nylon) and the like.

The polyacetal powder used in the present invention has a crystalline main chain composed of repeating methylene groups and oxygen atoms, and having at least one of two types of polyether structures represented by the following chemical formula 2. It is a thermoplastic resin. The melting point of such polyacetal is 175-18
1 ° C., coefficient of linear expansion 8.5 × 10 ⁻⁵ to 10 × 10 ⁻⁵ cm /
cm / ° C.

[0028]

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The above-mentioned polyamide or polyacetal is used as a powdery resin and has an average particle size of 25%.
Those having a size of 0 μm or less, preferably 10 to 250 μm can be employed. The reason is that even if a resin powder having a particle diameter of less than 10 μm is produced, the effect is not so different from that of a resin powder having a larger particle diameter, and practicality is low in terms of cost. This is because the strength is reduced.
In addition, a resin powder having a large particle size exceeding a predetermined particle size is not preferable because when the solid lubricant is injected into the inside of the bearing or the like, the tip (nozzle) of the injection tube is easily clogged.

The mixing ratio of such a powdery resin is 5 to 95% by weight of the whole mixture, and within this range, the required degree of oil separation, toughness and hardness are obtained according to the use of the solid lubricant. Adjust as follows. When the mixing ratio of the powdery resin is increased, the solid lubricant tends to be hard.

In order to mix the oil or grease described above with one or more powders selected from polyamide powder and polyacetal powder, and to keep these powders in a dispersed state, the powdery resin is mixed after mixing the materials. The solid lubricant is heated to a temperature higher than the gelling temperature and then cooled and solidified to about room temperature to obtain a solid lubricant having an oily surface (a surface from which oil seeps out).

When the lubricant mixed with the powdered resin is not a liquid oil at room temperature but a semi-solid lubricating grease at room temperature, the heating temperature of the mixture is higher than the gel point of the powdered oil or fat. It is preferable to uniformly disperse by employing a temperature below the grease drop point.

[0033]

EXAMPLES Raw materials used in Examples and Comparative Examples are collectively described below. All the mixing ratios of the raw materials shown in Table 1 are shown by weight%.

(1) 12 nylon (manufactured by Daicel Huls Co., Ltd .: diamide fine particle powder WS250P); (2) polyacetal (manufactured by Polyplastics: Duracon M25-44) (3) ultra-high molecular weight polyethylene (Mitsui Petrochemical Co., Ltd.) (4) Ester oil (alkyl phosphate ester) (5) Silicone oil (dimethylpolysiloxane) (6) Polyalkylene glycol oil (mixed oil of polyethylene glycol and polypropylene glycol) (7) Food machine grease I (Thickened with aluminum composite soap using liquid paraffin as base oil), (8) Grease for food machinery II (Thickened with polyurea using ester oil as base oil).

[Examples 1 to 6] The raw materials were mixed in the mixing ratio (% by weight) shown in Table 1, and the mixture was poured into an iron cylindrical container (inner diameter φ10 mm, height 8 mm). Iron plates were laid on the top and bottom and kept in a thermostat at 200 ° C. for 30 minutes. After cooling this to room temperature, the test piece taken out of the container was used as a test piece, and (a) a hardness test was performed as follows.
(B) A thermal deformation test, (c) a rust test and (d) a durability test were performed, and these results are also shown in Table 1.

(A) Hardness test Hs (spring hardness) was measured using a two-spring hardness tester specified in JIS S6050.

(B) Thermal Deformability Test The cylindrical test piece (diameter φ10 mm, height 8 mm) was observed for deformation with the naked eye in an atmosphere at 150 ° C., and there was no deformation (good) and deformation (bad). ) In two stages.

(C) Rust test The rust test method of ASTM D 1743 was further increased. That is, a radial load of 98N is applied to the bearing 6204, a running-in operation is performed at 1800 rpm for one minute, then 0.5% of a 3% saline solution is injected into the bearing, and then a radial load of 98N is applied again. In this state, it was rotated at 1800 rpm for 3 minutes. Thereafter, the bearing was placed in a desiccator and left at 40 ° C. for 100 hours, and the state of rust inside the bearing was examined. Evaluation of rusting status
The inner race is divided into 23 equal parts in the circumferential direction, and the outer race is divided into 31 equal parts in the circumferential direction.
The average number of sections for each test was defined as the rust score.

[0039]

[Table 1]

Comparative Example 1 Ultra-high molecular weight polyolefin,
Grease I for food machinery was mixed as a raw material at the compounding ratio shown in Table 2, and about 1.8 g of this was sealed in a bearing 6204 made of stainless steel (SUS440C) and sealed with rubber. Then, the bearing was heated in a thermostat at 150 to 180 ° C. for 30 minutes to solidify the mixture.

The obtained solid lubricant was used in the above (a)
A hardness test, a (b) heat deformation test and a (c) rust test were performed, and the results are shown in Table 1.

Comparative Example 2 About 1.8 g of food processing grease I was sealed in a bearing 6204 (SUJ2).

In order to examine the properties of the obtained solid lubricant, the above-mentioned (a) hardness test, (b) heat deformation test and (c) rust test were performed. The results are also shown in Table 1.

As is clear from the test results in Table 1, the solid lubricant of Comparative Example 1 in which the ultra-high molecular weight polyolefin and the grease were dispersed and maintained deformed in a 150 ° C. atmosphere, and were subjected to a durability test at 120 ° C. It was found that the service life reached in one hour, and the desired lubrication performance could not be exhibited in a bearing used at such a high temperature.

In Comparative Example 2 in which the grease was directly encapsulated without being solidified, the grease was deformed in an atmosphere of 150 ° C., and the result was also unsatisfactory in rust prevention.

On the other hand, in the first to sixth embodiments, the stainless steel bearing hardly rusts under severe conditions in which grease does not leak from the bearing and salt solution enters the inside of the bearing. The rust resistance and lubrication durability were extremely excellent, and the solid lubricant was not deformed in a high-temperature atmosphere at 150 ° C.

[0047]

As described above, the solid lubricant for food machinery of the present invention comprises a predetermined component which is safe and harmless to the human body, or a food to which a polyamide or polyacetal powder is added. Because it is a solid lubricant for machinery, it does not run off with water, does not deform even at 150 ° C or higher, withstands continuous use at high temperatures, and even when it comes into contact with salt water when lubricating metal sliding surfaces such as steel. There is an advantage that rust is hardly generated on the sliding surface.

Further, since the rolling bearing for food machinery of the present invention is filled with a solid lubricant composed of the above-mentioned predetermined components, rust is not formed on the sliding surface even under use conditions such as contact with water containing salt. There is an advantage that the rolling bearing is hard to generate, and can be used continuously at a high temperature of 120 ° C. or higher, and has excellent corrosion resistance and high-temperature durability.

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Claims (3)

[Claims] 1. A lubricating oil containing one or more oils selected from ester oils, silicone oils and polyalkylene glycol oils, or a grease based on this lubricating oil.
A solid lubricant for food machinery, which is obtained by heating a mixture of 95 to 5% by weight of a polyamide powder and 95 to 5% by weight of a polyamide powder at a temperature not lower than the gel point of the polyamide powder. 2. The solid lubricant for a food machine according to claim 1, wherein a polyacetal powder is used in place of the polyamide powder. 3. A rolling bearing for a food machine, wherein the solid lubricant for a food machine according to claim 1 is sealed in a rolling bearing made of stainless steel.