Preparation method of isocyanate

Abstract

The invention discloses a preparation method of isocyanate, and particularly provides a preparation method of a compound as shown in a formula II, which is characterized by comprising the following steps: in the presence of a solvent and a catalyst, cracking a compound as shown in a formula I to obtain the compound as shown in the formula II; the catalyst is KOH and / or ZnO. The preparation method provided by the invention has one or more of the following advantages: (1) no chloride is introduced; (2) the thermal cracking reaction temperature is low; (3) the catalyst is solid and is easy to separate; (4) few by-products are produced; # imgabs0 #

Description

Technical Field

[0001] The invention relates to a method for preparing isocyanate. Background Art

[0002] Isocyanates are an important class of organic reaction intermediates that have a wide range of uses in industry, agriculture, medicine and health. This class of compounds is widely used in the synthesis of polyisocyanates, polyurethanes, polyureas, polymer adhesives, pesticides, herbicides, etc.

[0003] At present, isocyanates are mainly prepared by reacting corresponding amine compounds with phosgene. Phosgene is a highly toxic compound, and a large amount of highly corrosive hydrogen chloride is generated during the reaction. Therefore, it can cause equipment corrosion, phosgene leakage, environmental pollution and personal injury. Summary of the invention

[0004] In order to solve the defects of the existing isocyanate preparation methods such as low yield, harsh reaction conditions and environmental pollution, the present invention provides a preparation method of a compound as shown in Formula II. The preparation method provided by the present invention has one or more of the following advantages: (1) no chloride-containing substances are introduced; (2) the thermal cracking reaction temperature is low; (3) the catalyst is solid and easy to separate; (4) there are few by-products; (5) mild reaction conditions; (6) low energy consumption; (7) low cost; and (8) environmental friendliness.

[0005] The present invention mainly solves the above technical problems through the following technical solutions.

[0006] The present invention provides a method for preparing a compound as shown in formula II, which comprises the following steps: in the presence of a solvent and a catalyst, cracking the compound as shown in formula I to obtain a compound as shown in formula II;

[0007] Where n is 1 or 2;

[0008] When n is 1, R is C1-C6 alkyl, C3-C6 cycloalkyl or C6-C 10 Aryl;

[0009] When n is 2, R is a C1-C6 alkylene group, a C3-C6 cycloalkylene group or a divalent C6-C 10 Aryl;

[0010] L is independently C1-C6 alkylene or L is absent;

[0011] R' is independently C1-C6 alkyl;

[0012] The catalyst is KOH and / or ZnO;

[0013] .

[0014] In some embodiments, when n is 1, R is ethyl, cyclohexane or phenyl, preferably phenyl.

[0015] In some embodiments, the R' is independently C1-C4 alkyl, preferably methyl.

[0016] In some embodiments, the L is independently C1-C4 alkylene, preferably isopropylidene.

[0017] In some embodiments, when n is 2, R is ethylene, cyclohexylene or a divalent phenyl group, preferably a divalent phenyl group.

[0018] In some embodiments, the compound represented by Formula I is represented by Formula IA, and the compound represented by Formula II is represented by Formula IIA; wherein R' is defined as described in any of the above schemes;

[0019] .

[0020] In the preparation of the compound shown in Formula II, the solvent is a conventional solvent for this type of reaction in the art, such as a hydrocarbon solvent, for example, C8-C 16 The alkane is preferably one or more of n-decane, n-octane and hexadecane; more preferably n-decane.

[0021] In some embodiments, in the preparation of the compound represented by Formula II, the catalyst is KOH.

[0022] In some embodiments, in the preparation of the compound of formula II, the mass ratio of the compound of formula I to the catalyst is 100:2-100:6, preferably 100:3-100:5, and further preferably 100:4.

[0023] In some embodiments, in the preparation of the compound of formula II, the mass-to-volume ratio of the compound of formula I and the solvent is 0.6-1.4 g / 10 ml, preferably 0.8-1.2 g / 10 ml, for example 1 g / 10 ml.

[0024] In some embodiments, in the preparation of the compound of formula II, the reaction temperature is 160-250°C, such as 190-220°C.

[0025] In some embodiments, in the preparation of the compound of Formula II, the reaction pressure is 0.9-1.2 atmospheres, such as normal pressure.

[0026] In some embodiments, in the preparation of the compound of formula II, the progress of the reaction can be monitored by conventional detection methods in the art (such as HPLC, TLC or NMR), and the disappearance of the compound of formula I is generally regarded as the reaction endpoint. The reaction time is generally 4-6 hours, for example 5 hours.

[0027] In some embodiments, in the preparation of the compound of Formula II, the materials for preparing the compound of Formula II are composed of the following: the compound of Formula I, the solvent and the catalyst.

[0028] In some embodiments, the preparation of the compound shown in Formula II further includes the following post-treatment step: after the reaction is completed, the temperature is controlled to 140-160° C., vacuum is drawn at a negative pressure of 0.08 MPa-negative pressure of 0.1 MPa, and the product is distilled to obtain the compound shown in Formula II. For example, after the reaction is completed, the temperature is controlled to 150° C., vacuum is drawn at a negative pressure of 0.1 MPa, and the product is distilled to obtain the compound shown in Formula II.

[0029] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0030] The reagents and raw materials used in the present invention are commercially available.

[0031] The positive and progressive effects of the present invention are:

[0032] (1) No chloride is introduced (2) The thermal cracking reaction temperature is low (3) The catalyst is solid and easy to separate (4) Few by-products (5) Mild reaction conditions (6) Low energy consumption (7) Low cost (8) Environmentally friendly.

[0033] Unless otherwise specified, the terms used in the present invention have the following meanings:

[0034] The term "alkyl" refers to a straight or branched chain alkyl group with a specified number of carbon atoms (e.g., C1 to C6). Alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.

[0035] The term "alkylene" refers to an alkyl group containing two chemical bonds that can be bonded to other atoms or molecules.

[0036] The term "cycloalkyl" refers to a saturated monocyclic ring group consisting only of carbon atoms with a specified number of carbon atoms (e.g., C3-C6). Cycloalkyl includes, but is not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc.

[0037] The term "cycloalkylene" refers to a cycloalkyl group that contains two chemical bonds to other atoms or molecules.

[0038] The term "aryl" refers to a group having a specified number of carbon atoms (e.g. C6~C 10 ) is a cyclic group with aromaticity composed only of carbon atoms, which is monocyclic or polycyclic, and at least one ring is aromatic (in accordance with Huckel's rule). The aryl group is connected to other fragments in the molecule through an aromatic ring or a non-aromatic ring. The aryl group includes but is not limited to phenyl, naphthyl, etc.

[0039] The term "divalent" refers to a molecule that contains two chemical bonds that can bind to other atoms or molecules. DETAILED DESCRIPTION

[0040] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0041] Example 1

[0042] Add 50g of tetramethyl meta-xylylene diurethane as reactant in a three-necked flask, add 4% catalyst KOH by weight of reactant, 500ml of n-decane as solvent, control the reaction temperature at 190 ~ 220℃ in an oil bath, perform thermal cracking, and end the reaction after 5 hours. Then cool to 150℃, evacuate and distill the mixed solution of all products and raw materials in the flask under negative pressure of 0.1MPa to obtain tetramethyl meta-xylylene diisocyanate with a yield of 90%.

[0043] Example 2

[0044] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 4% KOH catalyst by weight of the reactant was added. The reaction temperature was controlled at 220-250° C. in an oil bath. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 75%.

[0045] Example 3

[0046] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 4% KOH catalyst by weight of the reactant was added. The reaction temperature was controlled at 160-190° C. in an oil bath. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 65%.

[0047] Example 4

[0048] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 3% KOH catalyst by weight of the reactant was added. The reaction temperature was controlled at 190-220° C. in an oil bath. The other reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 85%.

[0049] Example 5

[0050] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 5% of the mass of the reactant as a catalyst KOH was added. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 88%.

[0051] Example 6

[0052] 50 g of tetramethyl meta-xylylene diurethane was added as a reactant in a three-necked flask, and 4% of the amount of the reactant was added as a catalyst KOH. The remaining reaction conditions and process were the same as those in Example 1, and the reaction was terminated after 4 hours to obtain tetramethyl meta-xylylene diisocyanate with a yield of 73%.

[0053] Example 7

[0054] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 4% of the amount of the reactant was added as a catalyst KOH. The remaining reaction conditions and process were the same as those in Example 1, and the reaction was terminated after 6 hours to obtain tetramethyl meta-xylylene diisocyanate with a yield of 81%.

[0055] Example 8

[0056] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and a catalyst ZnO was added which was 3% by weight of the reactant. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 79%.

[0057] Example 9

[0058] In a three-necked flask, 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant, 4% KOH catalyst by weight of the reactant, and 500 ml of n-octane was added as a solvent. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate in a yield of 83%.

[0059] Example 10

[0060] In a three-necked flask, 50 g of tetramethyl meta-xylylene diurethane was added as a reactant, 4% KOH catalyst by weight of the reactant, and 500 ml of hexadecane was added as a solvent. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 77%.

[0061] Comparative Example 1

[0062] 50 g of tetramethyl meta-xylylene dicarbamate was added as a reactant in a three-necked flask, and 10% of the mass of the reactant was added as a catalyst CaO. The remaining reaction conditions and process were the same as those in Example 1 to obtain tetramethyl meta-xylylene diisocyanate with a yield of 63%.

Claims

1. A method for preparing a compound as shown in formula II, characterized in that: It includes the following steps: In the presence of a solvent and a catalyst, the compound shown in Formula I is cracked to obtain a compound shown in Formula II; Where n is 1 or 2; When n is 1, R is C1-C6 alkyl, C3-C6 cycloalkyl or C6-C 10 Aryl; When n is 2, R is a C1-C6 alkylene group, a C3-C6 cycloalkylene group or a divalent C6-C 10 Aryl; L is independently C1-C6 alkylene or L is absent; R' is independently C1-C6 alkyl; The catalyst is KOH and / or ZnO; 。 2. The preparation method according to claim 1, characterized in that: It meets one or more of the following conditions: (1) n is 2; (2) The R' is independently a C1-C4 alkyl group; (3) L is independently C1-C4 alkylene; (4) R is ethylene, cyclohexylene or divalent phenyl.

3. The preparation method according to claim 1, characterized in that: It meets one or more of the following conditions: (1) R' is a methyl group; (2) L is isopropylidene; (3) The R is a divalent phenyl group.

4. The preparation method according to claim 1, characterized in that: The compound represented by formula I is represented by formula IA, and the compound represented by formula II is represented by formula IIA; wherein the definition of R' is as described in any one of claims 1 to 3; 。 5. The preparation method according to claim 1, characterized in that: The catalyst is KOH.

6. The preparation method according to claim 1, characterized in that: It meets one or more of the following conditions: (1) The mass ratio of the compound represented by formula I to the catalyst is 100:2-100:6; (2) The mass-to-volume ratio of the compound of formula I to the solvent is 0.6-1.4 g / 10 ml; (3) The reaction temperature is 160-250°C; (4) The reaction pressure is 0.9-1.2 atmospheres; (5) The solvent is a hydrocarbon solvent; (6) The reaction time is 4-6 hours.

7. The preparation method according to claim 1, characterized in that: It meets one or more of the following conditions: (1) The mass ratio of the compound represented by formula I to the catalyst is 100:3-100:5; (2) The mass-to-volume ratio of the compound of formula I to the solvent is 0.8-1.2 g / 10 ml; (3) The reaction temperature is 190-220°C; (4) The reaction pressure is normal pressure; (5) The solvent is C8-C 16 Alkanes; (6) The reaction time is 5 hours.

8. The preparation method according to claim 1, characterized in that: It meets one or more of the following conditions: (1) The mass ratio of the compound represented by formula I to the catalyst is 100:4; (2) The mass-to-volume ratio of the compound of formula I to the solvent is 1 g / 10 ml; (3) The solvent is one or more of n-decane, n-octane and hexadecane; for example, n-decane; (4) The material for preparing the compound represented by formula II is composed of the following: The compound as shown in formula I, the solvent and the catalyst.

9. The preparation method according to claim 1, characterized in that: It also includes the following post-treatment steps: after the reaction is completed, the temperature is controlled to 140-160° C., and the product is distilled under a vacuum of 0.08 MPa to 0.1 MPa to obtain a compound shown in formula II.

10. The preparation method according to claim 9, characterized in that: The post-treatment step is: after the reaction is completed, the temperature is controlled to 150° C., vacuum is drawn at a negative pressure of 0.1 MPa, and the product is distilled to obtain a compound as shown in Formula II.

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