JP7473378B2 - Lubricant composition for food machinery - Google Patents

Description

The present invention relates to a lubricant composition for use in food processing machines.

Conventionally, in food factories and factories that manufacture food-related parts, lubricant compositions are used on the bearings and sliding parts of food machinery. Food machinery also conceptually includes machines that package food, including clip packaging, and lubricant compositions are applied to parts that come into direct contact with the manufactured food and its packaging.

When applying for ISO 22000 (food safety management system) on-site management (HACCP) certification for lubricants used in food machinery, the lubricants must be H1 certified by an organization that certifies and registers chemical substances other than food ingredients used in food manufacturing plants, and can be used in places where there is a possibility of accidental contamination with food. Note that the National Sanitation Foundation International (NSF International), an official certification body of the American National Standards Institute (ANSI), has taken over the duties of the United States Department of Agriculture (USDA) since 2001 and is responsible for the certification.

In order to receive H1 certification from NSF International, the lubricant composition must be made of raw materials and ingredients that can be used for H1 certification, known as HX1 grade. Some raw materials in the HX1 grade have upper limits on their content, and there are limitations to the additive formulation in a wide variety of environments, especially in a wide range of temperatures from low to high (for example, -40°C to 200°C). Furthermore, the limitations of the additive formulation affect the life of the equipment due to the progression of wear, making it necessary to take measures to prevent wear, such as increasing the amount of grease, shortening the interval between grease applications, and increasing the use of specialized products, which increases the cost of use and makes management more complicated.

To address these issues, it is essential to increase the amount of HX1 grade raw materials used, which in turn limits the types of additives that are certified for HX1 grade.

In addition, if the lubricant composition applied to food machinery adheres to food packaging, it can be largely removed by cleaning on the production line, but a small amount may remain. In such cases, the small amount of remaining lubricant may discolor due to ultraviolet light, etc., causing stains on the packaging, significantly reducing the product value.

Although the technologies disclosed in Patent Documents 1 to 4, for example, are known as lubricant compositions for food machinery, there has been no proposal for a lubricant composition that can provide excellent lubricity without causing discoloration.

JP 2018-177921 A JP 2009-91502 A JP 2001-131569 A Japanese Patent Application Laid-Open No. 7-11280

The present invention has been proposed in light of these circumstances, and aims to provide a lubricant composition for food machinery that can be used in food machinery and that can provide excellent lubrication without causing discoloration.

The inventors of the present invention have conducted extensive research to solve the above-mentioned problems. As a result, they have discovered that a lubricant composition that contains a polyol ester together with a base oil and does not contain an amine-based antioxidant can provide excellent lubricity without causing discoloration, and have thus completed the present invention.

(1) The first aspect of the present invention is a lubricant composition for food processing machinery, which contains a base oil and a polyol ester, but does not contain an amine-based antioxidant.

(2) The second aspect of the present invention is a food machinery lubricant composition according to the first aspect of the present invention, which further contains a thiophosphate ester.

(3) The third invention of the present invention is a food processing machine lubricant composition according to the first or second invention, which contains a polyalphaolefin as the base oil.

(4) The fourth invention of the present invention is a food machinery lubricant composition according to the third invention, further comprising liquid paraffin as the base oil.

(5) The fifth aspect of the present invention is a food machinery lubricant composition according to any one of the first to fourth aspects, further comprising a thiophenol-based antioxidant.

The present invention provides a lubricant composition that can provide excellent lubricity without causing discoloration.

A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail below. Note that the present invention can be modified in various ways without departing from the spirit of the invention. Note that the present invention is not limited to the following embodiment, and can be modified as appropriate without departing from the spirit of the invention. In this specification, the expression "x to y" (x and y are arbitrary numbers) means "greater than or equal to x and less than or equal to y" unless otherwise specified.

<1. Lubricant composition for food machinery>
The lubricant composition according to the present embodiment is a lubricant composition for food machinery, which contains base oil and additives.Here, the food machinery is a machine used in a factory or the like for manufacturing food or food-related parts, and examples thereof include a grinder, a printer or a molding machine for containers, a robot reducer for a conveying line, a machine for manufacturing packaging paper, a freezer, etc.The lubricant composition for food machinery is a lubricant composition that is applied by coating on the bearings, sliding parts, etc. of these food machinery.

Specifically, the lubricant composition according to this embodiment is characterized by containing at least a base oil and a polyol ester, and not containing an amine-based antioxidant as an antioxidant. Such a lubricant composition can provide excellent lubricity without discoloration due to ultraviolet rays.

This lubricant composition can further contain additives such as antioxidants other than amine-based antioxidants, extreme pressure agents, and antiwear agents, which can impart superior properties such as rust prevention, water resistance, extreme pressure resistance, and wear resistance to the bearings and sliding parts of food processing machinery. A thickener can also be added as an additive, which can result in a semi-solid grease.

Below, we will explain in more detail each component that makes up the lubricant composition for food processing machinery.

[Base oil]
The base oil constituting the lubricant composition is not limited as long as it can be used in food processing machines, but preferably contains polyalphaolefin (polyαolefin, PAO). By using the base oil containing polyalphaolefin, it is possible to impart excellent lubricity. In addition, it is possible to maintain appropriate fluidity even in a wide range of temperature environments, especially in low temperature environments.

Specifically, polyalphaolefins are polymers of alphaolefins. From the viewpoints of viscosity index and volatility, the carbon number of the alphaolefin monomer is preferably about 6 to 20, more preferably about 8 to 16, and even more preferably about 10 to 14. Furthermore, from the viewpoints of low volatility and energy saving, polyalphaolefins are preferably dimers to pentamers of alphaolefins. The carbon number, compounding ratio, and degree of polymerization of the monomers can be adjusted according to the desired properties.

As the polymerization catalyst for alpha olefins, metallocene catalysts, _AlCl3 catalysts, Ziegler type catalysts, etc. can be used, and it is particularly preferable to use metallocene catalysts for polymerization. Polyalphaolefins polymerized using metallocene catalysts are inexpensive and have excellent low-temperature fluidity. As the metallocene catalyst, for example, a known combination of metallocene complexes can be used, and as the metallocene complex, a complex having a conjugated carbon 5-membered ring containing titanium, zirconium, hafnium, etc. can be used.

The polyalphaolefin preferably has a number average molecular weight of 400 to 3000, more preferably 700 to 2800, and particularly preferably 1000 to 2500. By including a polyalphaolefin with a number average molecular weight of 400 to 3000, it is possible to achieve higher stability, especially in extremely low temperature environments of around -40°C. It is also possible to effectively maintain the oil film strength, and further improve lubricity.

Moreover, the polyalphaolefin preferably has a kinetic viscosity of 50 mm ² /s or less at 40° C. By including a polyalphaolefin having a kinetic viscosity of 50 mm ² /s or less at 40° C., appropriate fluidity can be maintained even in a low-temperature environment, and the oil film strength can be maintained, thereby maintaining lubricity.

The content of polyalphaolefin in the base oil is not particularly limited, but is preferably about 20% to 100% by mass, and more preferably about 30% to 80% by mass, when the total amount of the base oil is 100% by mass. The content of polyalphaolefin in the lubricant composition is preferably in the range of about 15% to 60% by mass, and more preferably about 20% to 50% by mass, when the total amount of the lubricant composition is 100% by mass.

The polyalphaolefin is not limited to being made of a single type, but may be made of two or more types of polyalphaolefins with different molecular weights or two or more types of polyalphaolefins with different polymerization catalysts.

Here, the base oil can contain other base oil components. For example, liquid paraffin can be mentioned. Liquid paraffin is regulated in the regulation "FDA21CFR178.3570" as a substance that can be used as a lubricant under accidental food contact conditions. Therefore, liquid paraffin is highly safe for the human body even if it is accidentally mixed into the body, as long as the regulated values are observed. Liquid paraffin is also highly safe in that it is a substance that is also classified as an existing food additive under Japan's Food Sanitation Act.

In addition, because liquid paraffin is inexpensive, adding it to the base oil in a specified ratio makes it possible to create a lubricant composition that is inexpensive, has excellent lubricating properties, and is safer.

[Polyol ester (oil agent)]
The lubricant composition is characterized by containing a polyol ester as an oiliness agent. The polyol ester is an ester of a polyhydric alcohol (polyol) and a linear or branched, saturated or unsaturated fatty acid.

In this way, by including polyol ester as an oiliness agent, lubricity can be further improved. In addition, polyol ester has a high flash point and excellent high-temperature stability, and can provide excellent lubricity over a wide temperature range.

Specifically, in the polyol ester, for example, a polyol having a valence of 2 to 10, preferably 2 to 6, is used. For example, dihydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, and neopentyl glycol; glycerin, polyglycerin (e.g., diglycerin, triglycerin, tetraglycerin, etc.), trimethylol, etc. Examples of suitable polyhydric alcohols include polyols such as trimethylol ethane, trimethylol propane, trimethylol butane, pentaerythritol, 1,2,4-butane triol, 1,3,5-pentane triol, 1,2,6-hexane triol, 1,2,3,4-butane tetrol, sorbitol, sorbitan, sorbitol glycerin condensates, adonitol, arabitol, xylitol, and mannitol; and sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, and sucrose. Among these, in particular, from the viewpoint of obtaining higher thermal stability, neopentyl glycol, trimethylol ethane, trimethylol propane, pentaerythritol, dipentaerythritol, and mixtures thereof are more preferred. As polyols, partial esters of these polyhydric alcohols and linear or branched fatty acids can also be used.

The fatty acid may be, for example, a linear or branched, saturated or unsaturated fatty acid having 7 to 32 carbon atoms, and preferably a branched fatty acid. Specific examples include heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 2-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 2-ethyl-2-methylbutanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid, 2-ethylhexanoic acid, 2-ethylhexanoic acid, 2-methyloctanoic acid, 2,2-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, and 2,2-dimethyloctanoic acid. If the fatty acid constituting the polyol ester has less than 7 carbon atoms, it may not be possible to obtain excellent lubricity, while if the fatty acid has more than 32 carbon atoms, it may result in reduced fluidity, especially at low temperatures.

The polyol ester may be a complete ester in which all of the hydroxyl or carboxyl groups in the polyol are esterified, or a partial ester in which some of the hydroxyl or carboxyl groups remain unesterified.

The polyol ester preferably has a flash point of 280°C or higher, and more preferably 300°C or higher. By using a polyol ester with a flash point of 280°C or higher, high temperature stability can be further improved and evaporation loss can be further reduced. The upper limit is not particularly limited, but can be, for example, about 400°C or lower.

The polyol ester preferably has a pour point of -10°C or lower, and more preferably -20°C or lower. The pour point is a value measured in accordance with JIS K 2269. The polyol ester preferably has a kinetic viscosity at 40°C in the range of about ^64mm2 /s to ^500mm2 /s, which is preferable because it improves low-temperature fluidity.

The content of the polyol ester is not particularly limited, but is preferably about 3% to 50% by mass, more preferably about 5% to 30% by mass, and particularly preferably in the range of 10% to 25% by mass, when the total amount of the lubricant composition is 100% by mass. If the content of the polyol ester is less than 3% by mass, the effect of improving lubricity is not sufficiently obtained. On the other hand, if the content exceeds 55% by mass, the effect is not further improved and the production cost increases.

In addition, oily agents other than the polyol esters described above may be used in the lubricant composition depending on the purpose.

[Antioxidant]
The lubricant composition may contain an antioxidant. However, the lubricant composition according to the present embodiment is characterized in that it does not contain an amine-based antioxidant as the antioxidant.

As a result of the inventor's investigations, it was found that when an amine-based antioxidant is contained in a lubricant composition having the above-mentioned configuration, discoloration occurs when exposed to ultraviolet light. It is believed that such discoloration occurs because the amine-based antioxidant has the ability to absorb ultraviolet light, and forms a complex by absorbing ultraviolet light. In a lubricant composition used in food machinery, for example, when a lubricant adheres to a package that packages food, if the lubricant discolors due to ultraviolet light, the product value is reduced and the product becomes defective.

Based on this knowledge, the lubricant composition according to this embodiment is characterized by not containing an amine-based antioxidant. This makes it possible to suppress discoloration and prevent a decrease in product value.

"Amine antioxidant" refers to an antioxidant that has an amino group in the molecule. Also, "not contained" means that it is not intentionally contained, and that the content is intentionally set to 0% by mass.

On the other hand, the lubricant composition can contain antioxidants other than amine-based antioxidants. Specific examples include thiophenol-based antioxidants and phenol-based antioxidants. In particular, thiophenol-based antioxidants are relatively stable even when exposed to ultraviolet light, and exhibit stable antioxidant performance without discoloration.

For example, thiophenol-based oxidizing agents include thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and phenol-based antioxidants include hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,6-di-tert-butylphenol, and pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate].

The content of antioxidants other than amine-based antioxidants is not particularly limited, but is preferably about 0.05% by mass to 1% by mass, and more preferably about 0.1% by mass to 0.8% by mass, when the total amount of the lubricant composition is taken as 100% by mass.

[Extreme pressure agent]
Although not essential, it is preferred that the lubricant composition contains a thiophosphate ester as an extreme pressure agent, which can further enhance lubricity.

Various thiophosphates can be used, but it is preferable to use triphenyl phosphorothioate and butylated triphenyl phosphorothioate. In particular, it is preferable to contain a combination of triphenyl phosphorothioate and butylated triphenyl phosphorothioate in this lubricant composition. This can effectively improve extreme pressure properties and further improve evaporation resistance.

The content of the thiophosphate ester-based extreme pressure agent is not particularly limited, but is preferably about 0.01% to 0.5% by mass when the total amount of the lubricant composition is 100% by mass. If the content exceeds 0.5% by mass, it may not be possible to use the lubricant composition suitably for food processing machinery applications in terms of NSF H1 certification.

As an extreme pressure agent, in addition to the above-mentioned thiophosphate esters, for example, phosphate ester-based extreme pressure agents can also be used in combination. Various phosphate ester-based extreme pressure agents can be used, but it is preferable to use a mixture of amine C11-14 side chain alkyl, monohexyl and dihexyl phosphates.

[Other additives]
In addition to the above-mentioned components, the lubricant composition may further contain additives depending on the purpose. The content of these additives may also be determined arbitrarily depending on the required performance, but should not impair the performance of the above-mentioned components. Examples of additives include antiwear agents and rust inhibitors.

2. Method for producing lubricant composition
The lubricating oil composition for food machinery according to the present embodiment can be produced in the same manner as in the production of ordinary lubricant compositions.

Specifically, for example, a predetermined amount of each of the above-mentioned components is added to the base oil, and other additives are added as necessary and mixed by stirring. A known stirrer or the like can be used for stirring, and each component is pre-dispersed in the base oil by stirring and mixing, and then re-dispersed using a colloid mill. In this way, the lubricant composition can be produced using relatively inexpensive equipment without requiring particularly complicated steps or management of production conditions.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<<Examples and Comparative Examples>>
Lubricant compositions of Examples and Comparative Examples were prepared so as to have the compositions shown in the following Table 1. Specifically, each component was weighed out so as to have the blending amount (mass%) shown in the following Table 1, and these were added to a base oil and mixed with a stirrer while being heated to prepare each sample.

The components constituting the composition were as follows:
・Polyalphaolefin A: DYRASYN-164 (Ineos)
Polyalphaolefin B: SpectraSyn Plus6 (ExxonMobil)
・Polyalphaolefin C: "Synfluid PAO 8cSt" (manufactured by Chevron)
Metallocene PAO: DURASYN 174I (Ineos)
・Liquid paraffin: "KAYDOL" (SONNEBORN)
・Polyol ester: "Synative ES TMTC" (manufactured by BASF)
・Thiophenol-based antioxidant: "IRGONOX L115" (manufactured by BASF)
・Amine-based antioxidant: "IRGANOX L57" (manufactured by BASF)
- Thiophosphate ester: "IRGALUBE TPPT" (manufactured by BASF)
Phosphate ester amine salt: "IRGALUBE 349" (manufactured by BASF)

<About the evaluation test>
As an evaluation of the lubricant compositions prepared in the examples and comparative examples, a discoloration test was carried out to evaluate the occurrence of discoloration. In addition, a FALEX durability test was carried out to evaluate the lubricity. As reference examples, as shown in Table 1, a hydraulic oil (Reference Example 1) of commercial product A, a vegetable oil (Reference Example 2) of commercial product B, and a gear oil for food machinery (Reference Example 3) of commercial product C were used to carry out the same evaluation.

For the discoloration test, a nonwoven fabric was immersed in the prepared lubricant composition, and the nonwoven fabric with the lubricant composition was left in a storage cabinet at 25°C for three weeks, and the presence or absence of discoloration after leaving it was confirmed.

For the FALEX durability test, a FALEX PIN & Vee-Block tester was used to carry out the wear test under the following conditions: load: 100 lbs (445 N), speed: 9.8 m/s, time: not specified (stops when torque rises to 4.52 N-m or more), application method: pin dipped into sample, and the friction coefficient μ was measured.

<About the results>
The evaluation results are shown in Table 1 below.

Claims (4)

A lubricant composition for use in food processing machines, comprising:
Contains a base oil and a polyol ester,
Does not contain amine-based antioxidants.
Further containing a thiophenol-based antioxidant .
Lubricant composition for food machinery. Further containing a thiophosphate ester,
The food machinery lubricant composition according to claim 1. The base oil comprises a polyalphaolefin.
The lubricant composition for food machinery according to claim 1 or 2. The base oil further contains liquid paraffin.
The lubricant composition for food machinery according to claim 3.