CN111303373B - Low-chroma allophanate composition and preparation method and application thereof - Google Patents

Low-chroma allophanate composition and preparation method and application thereof Download PDF

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CN111303373B
CN111303373B CN202010115166.3A CN202010115166A CN111303373B CN 111303373 B CN111303373 B CN 111303373B CN 202010115166 A CN202010115166 A CN 202010115166A CN 111303373 B CN111303373 B CN 111303373B
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alcohol
composition
allophanate
diisocyanate
acetal
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CN111303373A (en
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王暖程
尚永华
石滨
王玉启
刘伟杰
苏黎明
任娟
黎源
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Wanhua Chemical Group Co Ltd
Wanhua Chemical Ningbo Co Ltd
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Wanhua Chemical Ningbo Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/73—Polyisocyanates or polyisothiocyanates acyclic
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
    • C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/2805—Compounds having only one group containing active hydrogen
    • C08G18/2815—Monohydroxy compounds
    • C08G18/282—Alkanols, cycloalkanols or arylalkanols including terpenealcohols
    • C08G18/2825—Alkanols, cycloalkanols or arylalkanols including terpenealcohols having at least 6 carbon atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
    • C08G18/3203—Polyhydroxy compounds
    • C08G18/3206—Polyhydroxy compounds aliphatic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/02—Polyureas

Abstract

The invention provides an allophanate composition, a preparation method and an application thereof, belonging to the technical field of preparation of polyisocyanate compositions. In the method, aliphatic diisocyanate and alcohol react in the presence of a catalyst, a prepolymer is obtained after the catalytic reaction is terminated, the allophanate composition is obtained by film evaporation of the prepolymer, and the mass content of acetal in the alcohol is controlled to be lower than 100 ppm. The color number of the allophanate composition obtained by the method is less than or equal to 40Hazen, and the dosage of the catalyst is obviously reduced. The allophanate composition has better aging resistance when being applied to paint.

Description

Low-chroma allophanate composition and preparation method and application thereof
Technical Field
The invention belongs to the field of isocyanate, and particularly relates to a low-chroma allophanate composition, and a preparation method and application thereof.
Background
Because the polyisocyanate has excellent performances of weather resistance, wear resistance, corrosion resistance and the like, the polyisocyanate is widely used in the industries of coatings, adhesives and elastomers, particularly in the paint industry, and comprises an isocyanurate group-containing polyisocyanate curing agent.
However, such compositions obtained by trimerization of isocyanates have a high viscosity, requiring dilution with large amounts of solvent, which does not meet the environmental requirements for reducing volatile organic compounds, and at the same time, the high viscosity limits the use of polyisocyanates in the aqueous field.
To achieve viscosity reduction, it is often necessary to sacrifice conversion and avoid the formation of high molecular weight polymers during the polymerization process. This approach has the disadvantage of a significant reduction in production efficiency, resulting in increased energy consumption and cost.
It is reported in US patent 4810820, US5124427, US5235018 that polyisocyanate compositions of low viscosity can be obtained by urethanization or trimerization in the presence of alcohols, the presence of allophanates being effective in reducing the viscosity of the compositions.
However, the greatest disadvantage of the above-described processes for preparing allophanate-containing compositions is the relatively high color of the allophanates obtained. The high color of allophanates greatly limits their field of application, in particular their use in appearance coatings such as paints.
The main reasons for the high color of allophanate compositions are the high synthesis process temperatures and the introduction of catalysts, especially the high amounts of the latter catalysts.
Microscopic species in the feedstock tend to be one of the major causes of higher catalyst incorporation. Previous researches focused on the quality improvement of the raw material aliphatic (alicyclic-containing) isocyanate, such as the reduction of impurities containing chlorine and bromine in the aliphatic isocyanate, such as hydrolyzed chlorine, monochloro products, dichlorinated products, products containing carbamoyl chloride structures, products containing carbamoyl bromide structures, and the like.
Although the aliphatic diisocyanate quality can be obviously improved by the methods, the prepared allophanate has reduced chroma, but the reduction amplitude is limited; meanwhile, the process for treating impurities in the high-activity isocyanate raw material is complex, and the difficulty in realizing industrialization is high.
Disclosure of Invention
The object of the present invention is to provide a process for the preparation of allophanates having a low color number. The method can obviously reduce the dosage of the catalyst in the reaction process aiming at the problems in the preparation process of the existing allophanate composition, so that the obtained allophanate composition has lower color number, and the allophanate composition has better aging resistance and yellowing resistance when being applied to paint.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a process for preparing an allophanate composition, in which an aliphatic diisocyanate is reacted with an alcohol in the presence of a catalyst to obtain a prepolymer after termination of the catalytic reaction, the prepolymer is subjected to thin-film evaporation to obtain the allophanate composition, and the mass content of acetal in the alcohol is controlled to be less than 100ppm, preferably less than 50ppm, more preferably less than 20ppm, and still more preferably less than 5 ppm.
The inventors have made a systematic study on the cause of the higher allophanate color number, and have surprisingly found that reducing the acetal component content in the starting alcohol is another direction to the problem of improving the allophanate color number, and have accordingly provided a practical industrial solution.
The acetal is mainly derived from the production and storage processes of alcohol, and the specific formation mechanism is as follows:
Figure BDA0002391270250000031
an oxygen-carbon-oxygen structure contained in the acetal, as a bidentate ligand, may coordinate or interact with cations in the catalyst to weaken the catalytic activity of the catalyst. In particular, when the alcohol contains a hydroxyl group attached to a primary carbon, the acetal structure contains an active hydrogen (see the following formula), which is acidic and further inhibits the catalytic action.
Figure BDA0002391270250000041
The invention researches the interaction between the acetal and the catalyst, reduces the amount of the catalyst by reducing the acetal content in the alcohol, thereby reducing the influence of the catalyst on the color number of the product and finally obtaining the allophanate composition with low chroma.
In the invention, the method for controlling the content of acetal in alcohol is to add CaCl into the alcohol2And NaBH4And/or treated by rectification to reduce the acetal content.
In some embodiments, CaCl is added separately to the alcohol2And NaBH4And keeping the reaction system at the set temperature, stirring and reacting for a certain time to obtain the alcohol with the reduced acetal content.
Adding CaCl to the alcohol as described above2And NaBH4The specific principle of the treatment protocol is shown below. Calcium chloride undergoes reversible alcoholysis to dissociate a small amount of HCI, and undergoes reversible hydrolysis with a small amount of water and an acetal structure in alcohol to generate aldehyde and ketone impurities, and the aldehyde and ketone impurities react with NaBH at the temperature of 0-30 DEG C4The raw material alcohol is obtained after irreversible reduction.
Figure BDA0002391270250000051
In the present invention, CaCl is added2And NaBH4When the treatment is carried out, 0.1 to 1.0 weight percent of calcium chloride and 10 to 500ppm of NaBH are added4Based on the total mass of the alcohol;
preferably, NaBH4The molar weight of the acetal is 0.9 to 1.0 time of the molar weight of the acetal, so as to ensure the safety of the process.
In the present invention, CaCl is added2And NaBH4When the treatment is carried out, the treatment temperature is 0-30 ℃ and the treatment time is 0.5-5 h.
In the invention, the pressure of the rectification treatment is 1-10kPa, the temperature at the bottom of the rectification tower is 90-130 ℃, the number of 5-12 tower plates is increased, and the reflux ratio is 1.0-3.0;
preferably, CaCl is added2And NaBH4After the treatment, the mass content of acetal in the alcohol is controlled to be less than or equal to 1ppm through further treatment by rectification.
In the invention, the content of the alcohol is 1-15% by weight of the total weight of the aliphatic diisocyanate and the alcohol.
In the invention, the alcohol is monohydric alcohol and/or dihydric alcohol;
preferably, the monohydric alcohol is selected from one or more of C1-C10 aliphatic alcohol, araliphatic alcohol, aromatic alcohol, aliphatic phenol, araliphatic phenol and aromatic phenol.
In the present invention, the monohydric alcohol is preferably present in the form of a linear, branched or cyclic alcohol or a phenol; the above-mentioned dihydric alcohol is not limited to the following, and examples thereof include ethylene glycol, 1, 3-propanediol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 5-pentanediol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 4-pentanediol, neopentyl glycol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 2-methyl-1, 3-propanediol, 3-methyl-1, 5-pentanediol, 2-methyl-1, 8-octanediol and 2, 2-diethyl-1, 3-propanediol.
In the present invention, the catalyst includes, but is not limited to, metal carboxylate and/or quaternary ammonium salt. In some examples, the polymerization catalyst may be selected from (i) hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, etc., salts of organic weak acids such as acetic acid, capric acid, etc.; (ii) hydroxides of hydroxyalkylammonium such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, and triethylhydroxyethylammonium, and salts of organic weak acids such as acetic acid and capric acid; (iii) and metal salts of alkyl carboxylic acids such as acetic acid, caproic acid, caprylic acid, and myristic acid, such as tin, zinc, lead, and bismuth. The catalyst is preferably a catalyst of type (iii), in a preferred embodiment the catalyst of type (iii) is a carboxylate salt of tin.
In the present invention, the catalyst is added in an amount of 0.001 wt% to 0.1 wt% based on the amount of the aliphatic diisocyanate, and the catalyst may be used as a pure substance or optionally dissolved in an alcohol at an arbitrary concentration.
In the present invention, the reaction temperature of the catalytic reaction is 30 to 150 ℃, preferably 80 to 120 ℃.
In the invention, the method for terminating the catalytic reaction is to add a catalyst poison;
preferably, the catalyst poison is selected from protic acids and/or acylating agents, preferably from one or more of phosphoric acid, benzoic acid, benzoyl chloride and dibutyl phosphate.
It will be appreciated by those skilled in the art that different types of polymerization catalysts may be used in the reaction system, resulting in different amounts of catalyst poisons. In the reaction system of the present invention, the catalyst poison is added in an amount such that the polymerization catalyst in the system loses activity.
In some embodiments, the process of catalyzing the reaction is: under the atmosphere of nitrogen, adding diisocyanate and alcohol into a reaction container for mixing, heating the system under stirring, and carrying out urethane reaction; maintaining the temperature and adding a catalyst; tracking and measuring the NCO% of the reaction solution, and adding a catalyst poison to terminate the reaction when the NCO% value is reduced to a target value; after the reaction liquid was filtered, the unreacted diisocyanate monomer was removed by a thin film evaporator to obtain the target allophanate composition.
Another object of the present invention is to provide an allophanate composition.
An allophanate composition obtained by the preparation method.
In the present invention, the allophanate composition:
a)Mn(number average molecular weight) of 700 or less, Mn being calculated by summing the molecular weights of the components together with the moles of components per total moles;
b) including but not limited to one or more of allophanate structures, carbamate structures, isocyanurate structures, uretdione structures and iminooxadiazinedione structures, wherein the molar concentration of the allophanate structures in the composition is greater than or equal to 30%;
c) the color number is less than or equal to 40Hazen, preferably less than or equal to 30Hazen, more preferably less than or equal to 20Hazen, and the meaning of "color number" can be referred to the color number determination method in GB/T3143-1982.
In the present invention, when the molar concentration of the above-mentioned allophanate structure is not less than 30% and the number average molecular weight of the allophanate composition is not more than 700, the allophanate composition of the present invention can exhibit a relatively low viscosity.
In the present invention, the aliphatic diisocyanate monomer content in the allophanate composition is less than 0.5% by weight.
In the present invention, the aliphatic diisocyanate is selected from aliphatic diisocyanates having 4 to 30 carbon atoms, preferably one or more selected from 1, 4-butane diisocyanate, 1, 5-pentane diisocyanate, 2, 4-trimethyl-hexamethylene-1, 6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane and 4, 4' -dicyclohexylmethane diisocyanate, and more preferably 1, 6-Hexamethylene Diisocyanate (HDI). HDI has good weather resistance and reactivity, and the viscosity of the obtained polyisocyanate composition tends to be low.
It is a further object of the present invention to provide an allophanate composition.
The allophanate composition obtained by the preparation method or the application of the allophanate composition is used as a polyisocyanate component in the field of polyurethane, preferably in oil-based polyurethane paint, aqueous polyurethane material and yellowing-resistant polyurethane material.
The allophanate composition prepared by the method can be used as a raw material of one-component and two-component polyurethane paint. A particularly preferred field of application of these allophanate compositions is their use as polyisocyanate component in two-component polyurethane paints. In this preferred use, the other reaction raw materials which can be mixed and dosed with the polyisocyanate composition of the invention may be selected from one or more of the polyhydroxy polyesters, polyhydroxy polyethers and polyhydroxy polyacrylates well known in polyurethane paint technology, and optionally low molecular weight polyols and/or polyaspartic esters.
All% referred to in the present invention are mass% unless otherwise specified; all ppm referred to are mass ppm unless otherwise specified.
The pressures referred to in the present invention are absolute pressures.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
(1) the obtained allophanate composition has lower color number (the color number is less than or equal to 40Hazen), and has better aging resistance and yellowing resistance when being applied to paint;
(2) the using amount of the catalyst in the reaction process can be obviously reduced to be less than 0.05 percent, and in most cases, the using amount of the catalyst is reduced to be less than 0.02 percent by weight, which is obviously lower than the using amount range of the catalyst in the prior art from 0.05 percent to 0.1 percent by weight;
(3) the low-activity alcohol treatment process is simpler and easy to realize industrialization.
Detailed Description
In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
The main raw material sources are as follows:
1, 6-hexamethylene diisocyanate,
Figure BDA0002391270250000101
HDI, wanhua chemistry;
1-hexanol with the purity of more than or equal to 99 percent and sigma aldrich;
1, 3-butanediol with the purity of more than or equal to 99 percent and sigma aldrich;
stannous isooctanoate with purity more than or equal to 97 percent and sigma aldrich;
benzyltrimethylammonium hydroxide solution (40 wt% methanol solution), sigma aldrich;
phosphoric acid, 85% aqueous solution, sigma aldrich;
polyaspartic acid esters, warfarin chemical;
CaCl2the purity is more than or equal to 99 percent, and the sigma-Aldrich is adopted;
NaBH4the purity is more than or equal to 98 percent, and the sigma-aldrich is obtained.
The detection method comprises the following steps:
according to the method of GB/T12009.4-1989, the NCO content is measured by a Switzerland 905 potentiometric titrator;
the invention is based on the method of GB/T3143-1982, and the color number is measured in a 50mm disposable rectangular cuvette by using LICO 400 of HACH Lange company;
the method is based on the GB/T18583-2008 method, and the residual monomer content in the reaction system is determined by Agilent GC-7890B gas chromatography manufactured by Agilent;
the dynamic viscosity related to the invention is obtained by adopting a Brookfield DV-I Prime viscometer and adopting an S21 rotor at 25 ℃;
drying (tack-free) test: GB/T1728;
and (3) testing the glossiness: GB/T9754;
ultraviolet aging resistance test: GB/T1865;
and (3) hardness testing: GB/T1730;
and (4) testing the adhesive force grade: GB/T9286;
mn (number average molecular weight) test: GB/T27843-;
molar concentration of allophanate Structure AVANCE400 from Bruker Biospin was used with deuterated chloroform CDCl3As a solvent, the concentration of the sample (polyisocyanate composition) was measured at 60%, 100MHz and scanning overnight13C nuclear magnetic resonance spectrum;
in the above measurement, the integrated value of the following signals is divided by the number of carbons measured, and each molar ratio is determined from the value:
isocyanurate group: the concentration of the lead-free acid is close to 148.6ppm,
allophanate group: in the vicinity of 154ppm of the total content of the active carbon,
a carbamate group: in the vicinity of 156.5ppm,
iminooxadiazinedione group: in the vicinity of 137.3ppm,
uretdione groups: about 157.5ppm of the total amount of the catalyst,
molar concentration of allophanate structure: (signal area near 154 ppm)/(signal area near 154ppm + signal area near 148.6/signal area near 3+137.3ppm + signal area near 156.5ppm + signal area near 157.5 ppm/2).
The main equipment is as follows:
a rectifying tower with the diameter of 25mm and the height of 1.0m and glass filler;
the reaction kettle has the volume of 2L and an anchor type stirring paddle and the rotating diameter of 70 mm.
Example 1
Rectification treatment of 1-hexanol: intermittent vacuum rectification under 5kPa, the bottom temperature of the rectification column is 95 ℃,8 tower plates are provided, and the reflux ratio is 1.3. After the work-up, a total of 1Kg of alcohol was obtained, with a concentration of acetal structures of 86 ppm.
800g of HDI as a starting diisocyanate and 60g of treated 1-hexanol were charged to a 2-liter reaction vessel under a nitrogen atmosphere and mixed, and the urethanization reaction was carried out while raising the temperature of the system to 90 ℃ under stirring for 1.5 hours. Thereafter, the temperature was maintained at 90 ℃ and 0.4g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added, and NCO% of the reaction solution was determined by follow-up. The reaction was stopped when the NCO% value had dropped to 40.1% by adding 0.06g of phosphoric acid. After the reaction liquid was filtered, unreacted HDI was removed using a thin film evaporator at a feed temperature of 100 ℃ under a separation temperature pressure of 160 ℃, under an absolute pressure of 50pa, and in a feed amount of 0.5Kg/h, to obtain an allophanate composition. The allophanate composition has a Mn of 540, a molar concentration of allophanate structures of 85%, a color number of 32Hazen, a diisocyanate monomer concentration of 0.15% by weight, an NCO% of 18.0% by weight and a viscosity at 25 ℃ of 110 mPas.
Example 2
Rectification treatment of 1-hexanol: intermittent vacuum rectification is carried out, the pressure is 7kPa, the temperature at the bottom of the rectification tower is 110 ℃, the number of 8 tower plates is increased, and the reflux ratio is 1.6. After the treatment, 1Kg of alcohol was obtained in total, with a concentration of acetal structures of 43 ppm.
800g of starting diisocyanate HDI and 60g of 1-hexanol (acetal structure concentration 43ppm) were charged into a 2-L reaction vessel under a nitrogen atmosphere to mix, and the urethanization reaction was carried out while raising the system temperature to 90 ℃ under stirring and maintaining it for 1.5 hours. Thereafter, the temperature was maintained at 90 ℃ and 0.4g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added to measure the NCO% of the reaction solution. The reaction was stopped when the% NCO value had dropped to 40.0% by adding 0.06g of phosphoric acid. The reaction solution was filtered. Unreacted HDI was removed using a thin-film evaporator at a feed temperature of 100 ℃ under a separation temperature and pressure of 160 ℃ under an absolute pressure of 50pa at a feed rate of 0.5 Kg/h. An allophanate composition was obtained with a Mn of 545, a molar concentration of allophanate structures of 83%, a color number of 27Hazen, a diisocyanate monomer concentration of 0.13% by weight, an NCO% of 18.0% by weight and a viscosity at 25 ℃ of 113 mPas.
Example 3
Treatment of 1-hexanol rectification: intermittent vacuum rectification is carried out, the pressure is 7kPa, the temperature at the bottom of the rectification tower is 110 ℃, the number of 8 tower plates is increased, and the reflux ratio is 2.0. After the treatment, 1Kg of alcohol was obtained in total, with an acetal structure concentration of 15 ppm.
800g of starting diisocyanate HDI and 60g of 1-hexanol (acetal structure concentration 15ppm) were charged into a 2-L reaction vessel under a nitrogen atmosphere to mix, and the urethanization reaction was carried out while raising the system temperature to 90 ℃ under stirring and maintaining it for 1.5 hours. Thereafter, the temperature was maintained at 90 ℃ and 0.4g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added to measure the NCO% of the reaction solution. The reaction was stopped when the NCO% value had dropped to 40.1% by adding 0.06g of phosphoric acid. After the reaction solution was filtered. Unreacted HDI was removed using a thin film evaporator. An allophanate composition was obtained with a Mn of 540, a molar concentration of allophanate structures of 85%, a color number of 20Hazen, a diisocyanate monomer concentration of 0.11% by weight, an NCO% of 18.0% by weight and a viscosity at 25 ℃ of 108 mPas.
Example 4
Rectification treatment of 1-hexanol: intermittent vacuum rectification is carried out, the pressure is 7kPa, the temperature at the bottom of the rectification tower is 110 ℃, the number of 8 tower plates is increased, and the reflux ratio is 2.0. After the treatment, 1Kg of alcohol was obtained in total, with an acetal structure concentration of 15 ppm.
800g of starting diisocyanate HDI and 60g of 1-hexanol (acetal structure concentration 15ppm) were charged into a 2-L reaction vessel under a nitrogen atmosphere to mix, and the urethanization reaction was carried out while raising the system temperature to 90 ℃ under stirring and maintaining it for 1.5 hours. Thereafter, while the temperature was maintained at 90 ℃, 0.16g of benzyltrimethylammonium hydroxide (40 wt%, methanol solution) was added to measure the NCO% of the reaction solution. When the NCO% value had dropped to 38.5%, 0.045g of phosphoric acid were added to terminate the reaction. After the reaction solution was filtered. Unreacted HDI was removed using a thin-film evaporator at a feed temperature of 100 ℃ under a separation temperature and pressure of 160 ℃ under an absolute pressure of 50pa at a feed rate of 0.5 Kg/h. An allophanate composition is obtained, Mn 645, molar concentration of allophanate structure 45%, color number 21Hazen, diisocyanate monomer concentration 0.15% by weight, NCO% equal to 20.5% by weight and viscosity at 25 ℃ of 510 mPas.
Example 5
Rectifying 1, 3-butanediol: intermittent vacuum rectification is carried out, the pressure is 1kPa, the temperature at the bottom of the rectification tower is 130 ℃, the number of 6 tower plates is increased, and the reflux ratio is 2.0. After the treatment, 1Kg of alcohol was obtained in total, with a concentration of acetal structures of 13 ppm.
800g of HDI as a starting diisocyanate and 12g of 1, 3-butanediol (acetal structure concentration: 13ppm) were charged into a 2L reaction vessel under a nitrogen atmosphere and mixed, and the temperature of the system was raised to 90 ℃ with stirring and kept for 1.5 hours to conduct a urethanization reaction. Thereafter, while the temperature was maintained at 85 ℃, 0.12g of benzyltrimethylammonium hydroxide (40 wt%, methanol solution) was added, and the NCO% of the reaction solution was measured. When the NCO% value had fallen to 42.0%, 0.033g of phosphoric acid was added to terminate the reaction. After the reaction solution was filtered. A thin film evaporator was used, the feed temperature was 100 ℃, the separation temperature pressure was 160 ℃, the absolute pressure was 50pa, and the feed amount was 0.5Kg/h, to remove unreacted HDI. An allophanate composition was obtained with a Mn of 610, a molar concentration of allophanate structures of 68%, a color number of 19Hazen, a diisocyanate monomer concentration of 0.14% by weight, an NCO% of 22.1% by weight and a viscosity at 25 ℃ of 750 mPas.
Example 6
Pretreatment of 1-hexanol: to 1000g of 1-hexanol (acetal structure 250ppm) was added 1.5g of CaCl, respectively2(0.15% by weight) and 0.035g of NaBH4(35ppm), the reaction system was kept at 25 ℃ and stirred for 1 h.
Rectification treatment of 1-hexanol: intermittent vacuum rectification is carried out, the pressure is 7kPa, the temperature at the bottom of the rectification tower is 110 ℃, the number of 8 tower plates is increased, and the reflux ratio is 2.0. A total of 900g of alcohol with an acetal structure concentration of 1ppm are obtained after the treatment.
800g of HDI as a starting diisocyanate and 60g of 1-hexanol (acetal structure concentration of 1ppm) were charged into a 2-L reaction vessel under a nitrogen atmosphere and mixed, and the temperature of the system was raised to 90 ℃ with stirring and kept for 1.5 hours to conduct urethanization. Thereafter, the temperature was maintained at 90 ℃ and 0.4g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added to measure the NCO% of the reaction solution. The reaction was stopped when the NCO% value had dropped to 40.2% by adding 0.06g of phosphoric acid. After the reaction solution was filtered. Unreacted HDI was removed using a thin-film evaporator at a feed temperature of 100 ℃ under a separation temperature and pressure of 160 ℃ under an absolute pressure of 50pa at a feed rate of 0.5 Kg/h. An allophanate composition is obtained with a Mn of 536, a molar concentration of allophanate structures of 85%, a color number of 15Hazen, a diisocyanate monomer concentration of 0.19% by weight, an NCO% of 18.1% by weight and a viscosity at 25 ℃ of 105 mPas.
Example 7
Pretreatment of 1-hexanol: to 1000g of 1-hexanol (acetal structure 250ppm) was added 8g of CaCl each2(0.8 wt.%) and 0.4g of NaBH4(400ppm), the reaction system was kept at 5 ℃ and stirred for 4.5 h. Without rectification, a total of 950g of alcohol were obtained by distillation under reduced pressure (pressure 10kpa, still bottom temperature 130 ℃ C.) with an acetal structure concentration of 5 ppm.
800g of starting diisocyanate HDI and 96g of 1-hexanol (acetal structure concentration 5ppm) were charged into a 2-L reaction vessel under a nitrogen atmosphere to mix, and the urethanization reaction was carried out while raising the system temperature to 90 ℃ under stirring and maintaining it for 1.5 hours. Thereafter, the temperature was maintained at 115 ℃ and 0.3g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added to measure the NCO% of the reaction solution. When the NCO% value had dropped to 37.5%, 0.045g of phosphoric acid were added to terminate the reaction. After the reaction solution was filtered. Unreacted HDI was removed using a thin-film evaporator at a feed temperature of 100 ℃ under a separation temperature and pressure of 160 ℃ under an absolute pressure of 50pa at a feed rate of 0.5 Kg/h. An allophanate composition is obtained with Mn of 695, a molar concentration of allophanate structures of 88%, a color number of 17Hazen, a diisocyanate monomer concentration of 0.17% by weight, an NCO% of 16.0% by weight and a viscosity at 25 ℃ of 180 mPas.
Comparative example 1
The preparation was carried out as in example 1, with the following differences: the 1-hexanol used had an acetal structure content of 250 ppm.
60g of the above-mentioned 1-hexanol and 800g of HDI were charged into a 2L reaction vessel under a nitrogen atmosphere and mixed, and the system temperature was raised to 90 ℃ with stirring and kept for 1.5 hours to conduct a urethanization reaction. Thereafter, the temperature was maintained at 90 ℃ and 0.8g of stannous isooctanoate (30 wt%, 1-hexanol solution) was added to measure the NCO% of the reaction solution. The reaction was stopped when the% NCO value had dropped to 40.1% by adding 0.12g of phosphoric acid. After the reaction solution was filtered. Unreacted HDI was removed using a thin-film evaporator at a feed temperature of 100 ℃ under a separation temperature and pressure of 160 ℃ under an absolute pressure of 50pa at a feed rate of 0.5 Kg/h. An allophanate composition was obtained, Mn 540, molar concentration of allophanate structure 85%, color number 68Hazen, diisocyanate monomer concentration 0.16% by weight, NCO% equal to 18.0% by weight and viscosity at 25 ℃ of 113 mPas.
It can be seen from the above examples 1 to 7 that, when aliphatic diisocyanates having an acetal content of < 100ppm are used, a product having an acetal content of < 100ppm is obtained<40Hazen color number light color allophanate; furthermore, as the acetal content of the starting diisocyanate decreases, the amount of catalyst used in the reaction system tends to decrease. As can be seen from examples 6 and 7, the alcohol passes through CaCl2、NaBH4After treatment, the allophanate composition can be used for allophanate synthesis, and a lighter color allophanate composition can be further obtained. While the alcohol used in comparative example 1 had an acetal content exceeding 100ppm, the content of the catalyst to be added was significantly increased, and finally, the catalyst having a high acetal content could not be obtained<40Hazen color number light-colored allophanate compositions.
Example 7(examples of use)
Allophanate composition 1, allophanate composition 6 and allophanate composition 1' obtained in example 1, example 6 and comparative example 1 were mixed with polyaspartic acid ester at an NCO/OH molar ratio of 1:1, respectively, and a mixed solvent of butyl acetate/xylene was added to dilute the mixture (wherein the content of the curing agent in the solution formed by the curing agent and butyl acetate/xylene was 40 wt%), to finally obtain a paint. The paints made from allophanate composition 1 and allophanate composition 6 are designated as paint 1 and paint 6, and the paint made from allophanate composition 1 'is designated as paint 1'. The results of the performance tests on the paint in terms of uv aging resistance, adhesion and the like are shown in table 1.
Table 1 paint performance test results
Figure BDA0002391270250000171
As can be seen from the results of comparing the properties in Table 1, the paint vehicle obtained by adding the low-color number allophanate composition effectively improves the ultraviolet aging resistance under the condition of ensuring that other properties are excellent, and is more excellent in ultraviolet aging resistance than the paint vehicle obtained by adding the high-color number allophanate composition.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (24)

1. A method for preparing allophanate composition, aliphatic diisocyanate reacts with alcohol in the presence of catalyst in this method, obtain the prepolymer after terminating the catalytic reaction, the prepolymer evaporates through the membrane and gets the said allophanate composition, characterized by, control the mass content of acetal in the said alcohol to be lower than 100 ppm;
the amount of the catalyst added is 0.005-0.02wt% of the amount of the aliphatic diisocyanate.
2. The method according to claim 1, wherein the mass content of acetal in the alcohol is controlled to be less than 50 ppm.
3. The method according to claim 2, wherein the mass content of acetal in the alcohol is controlled to be less than 20 ppm.
4. The production method according to claim 3, wherein the mass content of acetal in the alcohol is controlled to be less than 5 ppm.
5. The process according to any one of claims 1 to 4, wherein the acetal content in the alcohol is controlled by adding CaCl to the alcohol2And NaBH4Carrying out treatment and/or rectification treatment;
and/or adding CaCl2And NaBH4When the treatment is carried out, 0.1 to 1.0 weight percent of calcium chloride and 10 to 500ppm of NaBH are added4Based on the total mass of the alcohol;
and/or adding CaCl2And NaBH4When in treatment, the treatment temperature is 0-30 ℃ and the treatment time is 0.5-5 h;
and/or the pressure of the rectification treatment is 1-10kPa, the bottom temperature of the rectification tower is 90-130 ℃, the number of 5-12 tower plates is 5-12, and the reflux ratio is 1.0-3.0.
6. The method of claim 5, wherein CaCl is added2And NaBH4When processed, NaBH4The molar amount of (a) is 0.9 to 1.0 times the molar amount of acetal.
7. The method of claim 5, wherein CaCl is added2And NaBH4After the treatment, the mass content of acetal in the alcohol is controlled to be less than or equal to 1ppm through further treatment by rectification.
8. The method according to any one of claims 1 to 4, wherein the alcohol is contained in an amount of 1% to 15% based on the total weight of the aliphatic diisocyanate and the alcohol;
and/or the alcohol is a monohydric alcohol and/or a dihydric alcohol.
9. The method of claim 8, wherein the monohydric alcohol is selected from one or more of C1-C10 aliphatic alcohols, araliphatic alcohols, aromatic alcohols, aliphatic phenols, araliphatic phenols, and aromatic phenols.
10. The production method according to any one of claims 1 to 4, characterized in that the catalyst comprises a metal carboxylate and/or a quaternary ammonium salt.
11. The production method according to any one of claims 1 to 4, wherein the reaction temperature of the catalytic reaction is 30 to 150 ℃.
12. The method of claim 11, wherein the reaction temperature of the catalytic reaction is 80 to 120 ℃.
13. The method according to any one of claims 1 to 4, wherein the method for terminating the catalytic reaction is adding a catalyst poison.
14. The process according to claim 13, wherein the catalyst poison is selected from protic acids and/or acylating agents.
15. The method of claim 14, wherein the catalyst poison is selected from one or more of phosphoric acid, benzoic acid, benzoyl chloride, and dibutyl phosphate.
16. An allophanate composition obtained by the preparation process according to any one of claims 1 to 15.
17. The composition as claimed in claim 16, wherein the allophanate composition:
a) Mn(number average molecular weight) is less than or equal to 700;
b) comprises one or more of allophanate structure, carbamate structure, isocyanurate structure, uretdione structure and iminooxadiazinedione structure, wherein the molar concentration of the allophanate structure in the composition is more than or equal to 30 percent;
c) the chroma is less than or equal to 40 Hazen.
18. The composition as claimed in claim 17, wherein the allophanate composition has a color of 30Hazen or less.
19. The composition as claimed in claim 17, wherein the allophanate composition has a color of 20Hazen or less.
20. The composition according to one of claims 16 to 19, characterized in that the aliphatic diisocyanate monomer content in the allophanate composition is less than 0.5% by weight;
and/or the aliphatic diisocyanate is selected from aliphatic diisocyanate with 4-30 carbon atoms.
21. The composition of claim 20, wherein the aliphatic diisocyanate is selected from one or more of 1, 4-butane diisocyanate, 1, 5-pentane diisocyanate, 1, 6-hexamethylene diisocyanate, 2, 4-trimethyl-hexamethylene-1, 6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, and 4, 4' -dicyclohexylmethane diisocyanate.
22. The composition as recited in claim 21 wherein the aliphatic diisocyanate is selected from the group consisting of 1, 6-hexamethylene diisocyanate.
23. Use of an allophanate composition obtained by the preparation process according to any one of claims 1 to 15 or of an allophanate composition according to any one of claims 16 to 22, as a polyisocyanate component, in the polyurethane sector.
24. Use of an allophanate composition according to claim 23 as a polyisocyanate component in an oil polyurethane paint, an aqueous polyurethane material, a yellowing-resistant polyurethane material.
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