JPH06166770A - Hindered piperidine compound useful as stabilizer for organic material - Google Patents

Abstract

PURPOSE:To provide a stabilizer containing a specific hindered piperidine as an active ingredient, exhibiting a high stabilizing effect against photooxidation deterioration, and used for organic materials. CONSTITUTION:The objective stabilizer contains a compound of the formula (R1 is H, 1-10C alkyl, 1-10C alkoxy, 3-10C cycloalkyloxy, 7-18C arylalkoxy, OH, R2 is H, 1-18C alkyl; n is 2-12) such as 4-hydroxy-N-(2,2,6,6-tetramethyl-4- piperidyl)butaneamide as an active ingredient. The stabilizer is preferably added in an amount of 0.02-2 pts.wt. as the hindered piperidine compound to 100 pts.wt. of the organic material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stabilization of organic materials using a specific hindered piperidine compound.

[0002]

2. Description of the Related Art Organic materials such as polyethylene, polypropylene, polyvinyl chloride, polyurethane, various synthetic resins including ABS resin, natural or synthetic rubber, and paints are deteriorated by light and softened, embrittled or discolored. It is known that the physical properties thereof are remarkably deteriorated. Therefore, various light stabilizers have been developed and used in the past, but there is still a strong demand for new light stabilizers.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a compound which exhibits a high stabilizing effect against photooxidative deterioration of organic materials.

Another object of the invention is to stabilize organic materials with such compounds.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted research to develop a compound having an excellent stabilizing effect against photooxidative deterioration of organic materials, and as a result, a specific hindered piperidine compound was identified. Found to have excellent effects,
The present invention has been completed.

That is, the present invention provides a stabilizer for organic materials containing a hindered piperidine compound represented by the following formula (I) as an active ingredient.

[0007]

[Chemical 3]

In the formula, R ¹ represents hydrogen, alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, cycloalkyloxy having 3 to 10 carbons, arylalkoxy having 7 to 18 carbons, or a hydroxyl group, R ² represents hydrogen or alkyl having 1 to 18 carbons, and n represents an integer of 2 to 12.

The present invention also provides a method for stabilizing an organic material by blending the stabilizer with a stabilizing effective amount, and an organic material composition containing the stabilizer in the organic material. provide.

The compounds of the formula (I) in which R ¹ is alkyl, alkoxy, cycloalkyloxy, arylalkoxy or hydroxyl are novel. Therefore, the present invention is further represented by the formula (I), wherein R ¹ is alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, cycloalkyloxy having 3 to 10 carbons, and having 7 to 18 carbons. Arylalkoxy or hydroxyl group, R ² is hydrogen or alkyl having 1 to 18 carbons, and n is 2
To a hindered piperidine compound that is an integer of 12.

In the above formula (I) representing the hindered piperidine compound serving as the stabilizer component of the present invention, R ¹ is hydrogen, alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, and 3 to 10 carbons. Is cycloalkyloxy, arylalkoxy having 7 to 18 carbon atoms or hydroxyl group. Examples of alkyl include methyl, ethyl, propyl, butyl, hexyl and octyl, and examples of alkoxy include methoxy, ethoxy, propoxy,
Examples thereof include butoxy, hexyloxy, octyloxy, etc., examples of cycloalkyloxy include cyclohexyloxy, and examples of arylalkoxy include benzyloxy. Alkyl and alkoxy having 3 or more carbon atoms may be linear or branched. Among these, relatively preferable R ¹ is hydrogen, alkyl, alkoxy, cycloalkyloxy and hydroxyl group, and hydrogen, alkyl having 1 to 3 carbon atoms (especially methyl or ethyl), octyloxy and cyclohexyloxy are more preferable. preferable.

R ² in the formula (I) is hydrogen or alkyl having 1 to 18 carbons. Examples of alkyl here include methyl, ethyl, propyl, butyl, hexyl,
Octyl and the like are exemplified. The alkyl having 3 or more carbon atoms may be linear or branched. Among these, relatively preferable R ² is hydrogen and alkyl having 1 to 4 carbon atoms, and particularly preferable is the case where R ² is hydrogen.

In the formula (I), n is an integer of 2 to 12, and the alkylene represented by -C _n H _2n- may be linear or branched. Specific examples of the alkylene represented by —C _n H _2n — include ethylene and 1,2-
Alternatively, 1,3-propylene, 1,2-, 1,3- or 1,4-butylene, pentamethylene, 1-methylbutylene, hexamethylene, octamethylene and the like can be mentioned. Particularly, n is preferably in the range of 3 to 5.

Among the hindered piperidine compounds represented by the formula (I), particularly useful compounds are those in which R ¹ is hydrogen, alkyl, alkoxy or hydroxyl group, R ² is hydrogen or alkyl having 1 to 4 carbon atoms, and n. Especially preferred are compounds wherein R ¹ is hydrogen, methyl, ethyl or octyloxy.

EUR. J. MED. CHEM.-CHIM. THER., 20
(1985), 302-308, in particular page 303, 4-hydroxy-N- (2,2,6,6-tetramethyl-4-piperidyl) butanamide is described and represented by the above formula (I). The hindered piperidine compound can be produced according to the method described in this publication. That is, the hindered piperidine compound of the formula (I) has the following formula (II)

[0016]

[Chemical 4]

Where R ¹ and R ² have the meanings given above.

A 2,2,6,6-tetramethyl-4-piperidyl compound represented by the following formula (III)

[0019]

[Chemical 5]

(Wherein n has the above-mentioned meaning)

It can be produced by reacting a cyclic ester represented by:

Specific examples of the 2,2,6,6-tetramethyl-4-piperidyl compound represented by the formula (II) are as follows.

4-amino-2,2,6,6-tetramethylpiperidine, 4-amino-1,2,2,6,6-pentamethylpiperidine, 4-amino-1-methoxy-2,
2,6,6-tetramethylpiperidine, 4-amino-
2,2,6,6-tetramethyl-1-octoxypiperidine, 2,2,6,6-tetramethyl-4- (N-methylamino) piperidine, 1,2,2,6,6-pentamethyl- 4- (N-methylamino) piperidine, 1-methoxy-2,2,6,6-tetramethyl-4- (N-methylamino) piperidine, 2,2,6,6-tetramethyl-4- (N -Methylamino) -1-octyloxypiperidine, 4- (Nn-butylamino) -2,2,6
6-Tetramethylpiperidine, 4- (N-n-butylamino) -1,2,2,6,6-pentamethylpiperidine, 4- (N-n-butylamino) -1-methoxy-
2,2,6,6-tetramethylpiperidine, 4- (N-
n-butylamino) -2,2,6,6-tetramethyl-
1-octyloxypiperidine.

Further, specific examples of the cyclic ester represented by the formula (III) include β-propiolactone, γ-butyrolactone, γ- or δ-valerolactone, δ- or ε.
-Caprolactone and the like.

The reaction between the 2,2,6,6-tetramethyl-4-piperidyl compound represented by the formula (II) and the cyclic ester represented by the formula (III) is usually preferably carried out in a solvent. Solvents that can be used include alcohols such as methanol and ethanol, aromatic hydrocarbons such as benzene, toluene and xylene, chlorinated hydrocarbons such as chloroform and carbon tetrachloride, tetrahydrofuran, 1,
Examples thereof include ethers such as 4-dioxane.

In this reaction, 2, represented by the formula (II)
It is preferable to use the cyclic ester represented by the formula (III) in an equimolar or slightly excess amount with respect to the 2,6,6-tetramethyl-4-piperidyl compound. In terms of more generalized values, it is preferable to use the cyclic ester in an amount of about 1-fold mole to about 2-fold mole per mole of the 2,2,6,6-tetramethyl-4-piperidyl compound. ,
More preferably, the cyclic ester is used in the range of about 1.1 times to about 1.5 times the molar amount. The reaction is usually from 50 ° C to 13
The reaction proceeds in the range of 0 ° C, preferably 90 ° C to 110 ° C.
It is performed in the range of ° C. Further, this reaction usually proceeds under atmospheric pressure, but it may be carried out under pressure.

After completion of the reaction, the solvent used can be removed to isolate the hindered piperidine compound of formula (I). Moreover, you may refine | purify by a well-known method as needed.

Further, if necessary, R in the formula (I)
After obtaining a compound in which ¹ is hydrogen, according to a known method, for example, according to the method described in JP-A 1-190678, JP-A 60-237065, JP-A 1-113368, etc.
R ¹ can also be modified. For example, a compound of formula (I) in which R ¹ is hydrogen can be methylated with a mixture of formaldehyde and formic acid. Further, a compound in which R ¹ is hydrogen in the formula (I) can be hydroxylated by reacting it with an oxidizing agent such as hydroperoxide. Furthermore, by reacting a compound of formula (I) in which R ¹ is hydrogen with an alkane or a cycloalkane in the presence of an oxidizing agent,
It is also possible to introduce an alkoxy group or a cycloalkyloxy group.

Specific examples of the hindered piperidine compound represented by the formula (I) thus obtained include those shown below.

Compound A: 3-hydroxy-N- (2,
2,6,6-Tetramethyl-4-piperidyl) propionamide Compound B: 3-hydroxy-N- (1,2,2,6,6)
-Pentamethyl-4-piperidyl) propionamide Compound C: 3-hydroxy-N- (2,2,6,6-tetramethyl-1-octyloxy-4-piperidyl) propionamide Compound D: 3-hydroxy-N- (1-Cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) propionamide compound E: 4-hydroxy-N- (2,2,6,6-tetramethyl-4-piperidyl) butanamide compound F: 4-hydroxy-N- (1,2,2,6,6
-Pentamethyl-4-piperidyl) butanamide Compound G: 4-hydroxy-N- (2,2,6,6-tetramethyl-1-octyloxy-4-piperidyl) butanamide Compound H: 4-hydroxy-N- (1 -Cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) butanamide

Compound I: 5-hydroxy-N- (2,
2,6,6-Tetramethyl-4-piperidyl) pentanamide Compound J: 5-hydroxy-N- (1,2,2,6,6)
-Pentamethyl-4-piperidyl) pentanamide Compound K: 5-hydroxy-N- (2,2,6,6-tetramethyl-1-octyloxy-4-piperidyl) pentanamide Compound L: 5-hydroxy-N- (1 -Cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) pentanamide Compound M: 6-hydroxy-N- (2,2,6,6-tetramethyl-4-piperidyl) hexanamide Compound N: 6 -Hydroxy-N- (1,2,2,6,6
-Pentamethyl-4-piperidyl) hexanamide Compound O: 6-hydroxy-N- (2,2,6,6-tetramethyl-1-octyloxy-4-piperidyl) hexanamide Compound P: 6-hydroxy-N- (1 -Cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) hexanamide

Among the hindered piperidine compounds represented by the formula (I), R ¹ is alkyl, alkoxy, cycloalkyloxy, arylalkoxy or hydroxyl group, R ² is hydrogen or alkyl, and n is 2 to 12 Compounds that are integers of are important. Above all,
Of particular importance are those in which R ¹ is alkyl having 1 to 3 carbons, octyloxy or cyclohexyloxy, those in which R ² is hydrogen and those in which n is 3 to 5.

The hindered piperidine compound represented by the formula (I) is effective for stabilizing various organic materials, particularly those having a property of being deteriorated by light. The following may be mentioned as specific examples of the organic material that can be stabilized, and they are effective for stabilizing a single substance or a mixture of two or more types.

(1) Polyethylene, such as low density polyethylene (LD-PE), high density polyethylene (HD-P)
E), linear low density polyethylene (LLD-PE); (2) polypropylene; (3) methylpentene polymer; (4) EEA (ethylene / ethyl acrylate copolymer) resin; (5) ethylene / vinyl acetate copolymer resin (6) Polystyrenes such as polystyrene, poly (p
-Methylstyrene), poly (α-methylstyrene); (7) AS (acrylonitrile / styrene copolymerization) resin; (8) ABS (acrylonitrile / butadiene / styrene copolymerization) resin; (9) AAS (special acrylic rubber / (Acrylonitrile / styrene copolymerization) resin; (10) ACS (acrylonitrile / chlorinated polyethylene /
Styrene copolymer) resin;

(11) Chlorinated polyethylene, polychloroprene, chlorinated rubber; (12) Polyvinyl chloride, polyvinylidene chloride; (13) Methacrylic resin; (14) Ethylene / vinyl alcohol copolymer resin; (15) Fluorine resin (16) Polyacetal; (17) Grafted polyphenylene ether resin and polyphenylene sulfite resin; (18) Polyurethane; (19) Polyamide; (20) Polyethylene terephthalate, Polybutylene terephthalate; (21) Polycarbonate; (22) Polyacrylate (23) Polysulfone, polyetheretherketone, polyethersulfone; (24) Aromatic polyester resin; (25) Epoxy resin; (26) Diallyl phthalate prepolymer; (27) Silicone resin; (28) Unsaturated polyester resin (29) Acrylic modified benzoguanamine resin; (30) Benzo Anamin / melamine resins; (31) urea resins;

(32) polybutadiene; (33) 1,2-polybutadiene; (34) polyisoprene; (35) styrene / butadiene copolymer; (36) butadiene / acrylonitrile copolymer; (37) ethylene / propylene copolymer Polymer; (38) Silicone rubber; (39) Epichlorohydrin rubber; (40) Acrylic rubber; (41) Natural rubber;

(42) Chlorine rubber paint; (43) Polyester resin paint; (44) Urethane resin paint; (45) Epoxy resin paint; (46) Acrylic resin paint; (47) Vinyl resin paint; (48) Amino Alkyl resin paint; (49) Alkyd resin paint; (50) Nitrocellulose resin paint; (51) Oil paint; (52) Wax; (53) Lubricating oil.

The stabilizer containing the hindered piperidine compound of formula (I) as an active ingredient is blended in a stabilizing effective amount with respect to the organic material, and the preferable addition amount naturally varies depending on the kind of the target organic material. But usually organic material 10
It is preferable to use the hindered piperidine compound of the formula (I) in an amount of about 0.01 to 5 parts by weight based on 0 part by weight. More preferably, the amount of the hindered piperidine compound of the formula (I) is 0.02 with respect to 100 parts by weight of the organic material.
It is used in the range of about 2 parts by weight.

According to the present invention, the organic material composition containing the hindered piperidine compound of the formula (I) may further contain other additives such as a phenolic antioxidant, if necessary.
Sulfur-based antioxidants, phosphorus-based antioxidants, ultraviolet absorbers, hindered amine-based light stabilizers other than formula (I), lubricants, plasticizers, flame retardants, nucleating agents, metal deactivators, antistatic agents, It may also contain pigments, inorganic fillers and the like.
These additives can, of course, be compounded at the same time as the hindered piperidine compound of the formula (I), or can be compounded at a stage separate from the hindered piperidine compound.

A hindered piperidine compound of formula (I),
Alternatively, in addition to the above, other optional additives may be added to the organic material by any known method and apparatus for obtaining a homogeneous mixture. For example, if the organic material is a solid polymer,
It can be blended directly with the polymer or it can be incorporated into the solid polymer in the form of a masterbatch. In addition, when the organic material is a synthetic polymer, it can be compounded in the form of a solution or a dispersion in a polymer solution during or immediately after the polymerization. On the other hand, when the organic material is a liquid such as oil, the hindered piperidine compound (I) or further any additive can be directly added and dissolved, and the hindered piperidine compound (I) or further arbitrary can be added. It is also possible to add the above-mentioned additive in a state of being dissolved or suspended in a liquid medium.

[0041]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition,% and parts in the examples are based on weight unless otherwise specified.

Example 1: 4-hydroxy-N- (2,
Preparation of 2,6,6-tetramethyl-4-piperidyl) butanamide (Compound E)

In a 500 ml four-necked flask, 50 g of 4-amino-2,2,6,6-tetramethylpiperidine (3
2 mmol), 30 g (35 mmol) of γ-butyrolactone and 400 ml of toluene. This mixture was reacted under reflux at 110 ° C. for about 10 hours. Then, when cooled with stirring, white crystals were precipitated. This was separated by filtration and dried to obtain 59 g (24 mmol) of the title compound.

Mass spectrometry (FD-MS): m / z 242 (M) ⁺ elemental analysis: C ₁₃ H ₂₆ N ₂ O ₂ calculated value C 64.4%; H 10.8%; N 11.6% measured value C 64.3%; H 10.7%; N 11.5% Melting point: 159-162 ° C

[0045] IR (KBr):. 3290 ( OH); 1650 (C = O) cm -1 1 H-NMR (270 MHz, CD 3 OD): δ 1.0-1.1
(m, 2H); 1.14 (s, 6H); 1.24 (s, 6H); 1.76 (dd, J =
12.7 and 3.9, 2H); 1.80 (tt, J = 7.4 and 6.1,
2H); 2.24 (t, J = 7.4, 2H); 3.56 (t, J = 6.1, 2H);
4.12 (tt, J = 12.5 and 3.9, 1H) ppm. ¹³ C-NMR (67.8 MHz, CD ₃ OD): δ 28.4; 3
0.2; 34.2; 34.7; 43.6; 45.7; 52.7; 62.6; 175.3 pp
m.

Example 2: 5-hydroxy-N- (2,
Preparation of 2,6,6-tetramethyl-4-piperidyl) pentanamide (Compound I)

The title compound was obtained by using δ-valerolactone in the same mole instead of γ-butyrolactone in Example 1.

Mass spectrometry (FD-MS): m / z 256 (M) ⁺ Elemental analysis: C ₁₄ H ₂₈ N ₂ O ₂ Calculated value C 65.6%; H 11.0%; N 10.9% Measured value C 65.1%; H 10.7%; N 10.4% Melting point: 131-133 ° C

IR (KBr): 3290 (OH); 1650 (C = O) cm ^-1 H-NMR (270 MHz, CD ₃ OD): δ 1.0-1.1
(m, 2H); 1.14 (s, 6H); 1.24 (s, 6H); 1.5-1.7 (m, 4
H); 1.76 (dd, J = 12.9 and 3.8, 2H); 2.18 (t, J
= 7.3, 2H); 3.55 (t, J = 6.4, 2H); 4.17 (tt, J = 1
2.2 and 3.8, 1H) ppm. ¹³ C-NMR (67.8 MHz, CD ₃ OD): δ 23.8; 2
8.3; 33.4; 34.6; 37.2; 43.5; 45.7; 52.7; 62.8; 175.
4 ppm.

Example 3: 6-hydroxy-N- (2,
Preparation of 2,6,6-tetramethyl-4-piperidyl) hexanamide (Compound M)

The title compound was obtained by using the same mole of ε-caprolactone instead of γ-butyrolactone in Example 1.

Mass Spectrometry (FD-MS): m / z 270 (M) ⁺ Elemental Analysis: C ₁₅ H ₃₀ N ₂ O ₂ Calculated C 66.6%; H 11.2%; N 10.4% Found C 66.8%; H 11.0%; N 10.1% Melting point: 120-122 ° C

[0053] IR (KBr):. 3300 ( OH); 1650 (C = O) cm -1 1 H-NMR (270 MHz, CD 3 OD): δ 1.0-1.1
(m, 2H); 1.14 (s, 6H); 1.24 (s, 6H); 1.3-1.7 (m, 6
H); 1.76 (dd, J = 12.9 and 3.8, 2H); 2.17 (t, J
= 7.4, 2H); 3.54 (t, J = 6.6, 2H); 4.17 (tt, J = 1
2.2 and 3.8, 1H) ppm. ¹³ C-NMR (67.8 MHz, CD ₃ OD): δ 26.8; 2
7.2; 28.3; 33.6; 34.6; 37.5; 43.5; 45.7; 52.7; 63.
1; 175.6 ppm.

Example 4: 6-Hydroxy-N- (1,
Production of 2,2,6,6-pentamethyl-4-piperidyl) hexanamide (Compound N)

Example 3 in a 200 ml four-necked flask.
10 g (39 mmol) of 6-hydroxy-N- (2,2,6,6-tetramethyl-4-piperidyl) hexanamide obtained in (4) and 100 ml of toluene were charged. Here
2.3 g (50 mmol) of formic acid and 4.3 g (53 mmol) of 37% formalin were added dropwise. Then, it was reacted for 2 hours while azeotropically dehydrating. The reaction solution was cooled, washed with a 1% aqueous sodium hydroxide solution and then concentrated to obtain 10 g (37 mmol) of the title compound.

Mass spectrometry (FD-MS): m / z 284 (M) ⁺ elemental analysis: C ₁₆ H ₃₂ N ₂ O ₂ calculated C 67.6%; H 11.3%; N 9.8% found C 66.7%; H 11.1%; N 9.1%

[0057] IR (liquid film):. 3350 (OH); 1660 (C = O) cm -1 1 H-NMR (270 MHz, CD 3 OD): δ 1.08 (s,
6H); 1.13 (s, 6H); 1.2-1.3 (m, 2H); 1.3-1.7 (m, 6
H); 1.78 (dd, J = 12.5 and 4.0, 2H); 2.16 (t, J
= 7.4, 2H); 2.24 (s, 3H); 3.64 (t, J = 6.4, 2H); 4.1
5 (tt, J = 12.2 and 4.0, 1H) ppm. ¹³ C-NMR (67.8 MHz, CD ₃ OD): δ 20.6; 2
6.4; 26.7; 28.6; 33.1; 33.3; 37.0; 41.9; 47.4; 56.
2; 62.4; 174.5 ppm.

Example 5: Weather resistance test of polypropylene

[Composition] Unstabilized polypropylene 100 parts Calcium stearate 0.05 part Test compound 0.1 part

The above mixture was melt-kneaded at 230 ° C. by a 30 mmφ single-screw extruder and pelletized. The pellets were molded by an injection molding machine at 230 ° C. to form a 1 mm thick sheet, which was used as a test piece. This test piece was placed in a sunshine weather au meter (light source: carbon arc) and irradiated with light under the conditions of a black panel temperature of 63 ° C. and a spray cycle of 12 minutes / 60 minutes, and a crack was generated on the light irradiation surface of the test piece. The weather resistance was evaluated by the time taken to complete. The results are shown in Table 1.

[0061]

[Table 1]

[0062]

The stabilizer of the present invention exhibits excellent performance against various organic materials such as thermoplastic resins such as polyolefin. In particular, it is effective for an organic material having a property of being deteriorated by light. For example, a resin containing this stabilizer is stable against photooxidation deterioration and becomes a high quality product.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tetsuo Yamaguchi 3-98 Kasugade, Konohana-ku, Osaka Sumitomo Chemical Co., Ltd.

Claims (10)

[Claims] 1. The formula: (Wherein R ¹ represents hydrogen, alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, cycloalkyloxy having 3 to 10 carbons, arylalkoxy having 7 to 18 carbons, or R ² Represents hydrogen or alkyl having 1 to 18 carbon atoms, and n represents an integer of 2 to 12), and is a stabilizer for organic materials containing a hindered piperidine compound as an active ingredient. 2. R ¹ is hydrogen, alkyl having 1 to 3 carbons,
The stabilizer according to claim 1, which is octyloxy or cyclohexyloxy. 3. The stabilizer according to claim 1, wherein R ² is hydrogen. 4. The method of claim 1, 2 or 3 wherein n is 3 to 5.
Stabilizer as described. 5. A method for stabilizing an organic material, comprising adding the stabilizer according to any one of claims 1 to 4 to the organic material in a stabilizing effective amount. 6. A stabilized organic material composition comprising an organic material containing the stabilizer according to any one of claims 1 to 4. 7. The formula: (In the formula, R ¹ represents alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, cycloalkyloxy having 3 to 10 carbons, arylalkoxy having 7 to 18 carbons or a hydroxyl group, and R ² is hydrogen. Or 1 to 1 carbon atoms
8 represents an alkyl, and n represents an integer of 2 to 12). 8. The compound according to claim 7, wherein R ¹ is alkyl having 1 to 3 carbons, octyloxy or cyclohexyloxy. 9. The compound according to claim 7, wherein R ² is hydrogen. 10. The compound according to claim 7, 8 or 9, wherein n is 3 to 5.