Adhesive composition and wooden mould pressing tray

Abstract

The invention belongs to the technical field of adhesives and molded trays, and particularly relates to an adhesive composition and a wooden molded tray. The adhesive composition comprises the following components in percentage by mass: 20%-70% of isocyanate; 10%-50% of a polycondensate; 10%-40% of a diluent; wherein the polycondensate is a polycondensate of anhydride containing a benzene ring, unsaturated fatty acid and micromolecular polyol, and the molecular weight polydispersity coefficient of the polycondensate is 1.5-4.0. The polycondensate with specific composition and molecular weight polydispersity coefficient is introduced into the adhesive composition, so that the flexibility of a whole cured product chain segment is increased, the whole toughness of the molded tray is improved, the operation stability of the tray in the using process is facilitated, and the whole bending strength of the molded tray is obviously improved compared with that of the molded tray without the polycondensate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adhesives and molded pallets, and particularly relates to an adhesive composition and a wooden molded pallet. BACKGROUND

[0002] With the rapid development of the packaging industry, pallets, as an important packaging form, play an irreplaceable role in modern logistics. Molded pallets are a new and important form of pallets, with the main advantages of low carbon, environmental protection, high strength, durability, and multiple applications, which can meet the needs of handling and storage in ports, yards, warehouses, workshops, and shopping malls. In recent years, they have received widespread attention.

[0003] Molded pallets are a new product made from wood, straw, peanut shells, cotton rods, and bamboo, which are crushed, cut into shavings, dried, and then molded into a new product by applying a certain adhesive under high temperature and pressure. The molded pallets in the prior art have insufficient toughness and too high rigidity, resulting in excessive brittleness and low bending strength of the pallet. In actual use, a large number of quality problems occur, especially during the forklift picking and transfer process and the long-distance sea transport process, due to excessive impact caused by jolting and insufficient toughness, which causes the pallet to deform under pressure, resulting in obvious brittle fracture and affecting the service life of the molded pallet.

[0004] To improve the problem of insufficient toughness of isocyanate adhesive molded pallets, the prior art introduces a polyether polyol and a special small molecule compound into the isocyanate reaction to increase the soft segment of isocyanate and achieve soft and hard combination, but the cost of small molecule compounds is generally high. Another patent document introduces a siloxane segment into the isocyanate adhesive system to improve the molecular flexibility and further improve the problem of insufficient toughness of molded pallets, but there is a problem of insufficient thermal stability. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the defects of high rigidity and insufficient toughness of the molded pallets in the prior art, thereby providing an adhesive composition and a molded pallet.

[0006] To this end, the present application provides the following technical solutions:

[0007] According to one aspect of the present application, an adhesive composition is provided, which comprises the following components by mass percentage: isocyanate 20%-70%; condensate 10%-50%; diluent 10%-40%;

[0008] The condensate is a condensate of an acid anhydride containing a benzene ring and an unsaturated fatty acid and a small molecule polyol, and the molecular weight polydispersity coefficient of the condensate is 1.5-4.0.

[0009] In some alternative embodiments, the composition comprises the following mass percentage of components: isocyanate 40%-60%; polycondensate 20%-30%; diluent 20%-40%.

[0010] In some alternative embodiments, the composition comprises the following mass percentage of components: isocyanate 40%-60%; polycondensate 20%-30%; diluent 20%-40%.

[0011] In some alternative embodiments, the composition comprises the following mass percentage of components: isocyanate 40%-60%; polycondensate 20%-30%; diluent 20%-40%.

[0012] In some alternative embodiments, the polycondensate is prepared by the following method comprising the following steps:

[0013] S1, in a protective atmosphere, the unsaturated fatty acid and the small molecule polyol are reacted under the catalysis of an alkaline catalyst, the reaction temperature is 180-220°C, and the reaction is stopped when the mutual solubility ratio of the product and ethanol is 2-6;

[0014] S2, the benzene ring-containing anhydride and the water-containing solvent are added and reacted at 180-200°C, the molecular weight polydispersity coefficient of the polycondensate is monitored, and the reaction is stopped when the standard is met.

[0015] In some alternative embodiments, in S1, the alkaline catalyst comprises at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide;

[0016] and / or, the alkaline catalyst is used in an amount of 0.1%-0.5% based on the total mass of the unsaturated fatty acid, the small molecule polyol, and the benzene ring-containing anhydride;

[0017] and / or, the reaction is stopped when the mutual solubility ratio of the product and ethanol is 3-5;

[0018] and / or, in S2, the water-containing solvent comprises at least one of xylene, benzene, toluene, xylene, and cyclohexane.

[0019] In some alternative embodiments, the benzene ring-containing anhydride comprises at least one of phthalic anhydride, terephthalic anhydride, trimellitic anhydride, and pyromellitic dianhydride;

[0020] and / or, the unsaturated fatty acid comprises at least one of linseed oil, tung oil, castor oil, catalpa oil, soybean oil, coconut oil, and palm oil;

[0021] And / or, the small molecule polyol has a molecular weight of 10-200 and a functionality of 2-4; optionally, the small molecule polyol includes at least one of ethylene glycol, 1,2-propanediol, 1,4-butanediol, diethylene glycol, glycerol;

[0022] And / or, the isocyanate includes at least one of polymethylene polyphenyl polyisocyanate and / or derivatives thereof; optionally, the isocyanate has an NCO value of 25-33% and a viscosity of 50-2000 cp at 25°C;

[0023] And / or, the diluent includes at least one of dichloromethane, dichloroethane, ethyl acetate, chlorobenzene.

[0024] In the present application, the isocyanate component is conventionally in the art, and can be at least one of the Wannate series polyisocyanates of Wanhua Chemical Group Co., Ltd., for example, PM-100, PM-200, PM-400, PM-600, PM-700, CW20, CW30, PM300E, 9132FC, etc.

[0025] Specifically, the preparation method of the polycondensate can include the following steps:

[0026] Step 1: Unsaturated fatty acid and small molecule polyol are injected into a four-necked flask, an alkaline catalyst is added, and the reaction is carried out by heating to 180-220°C under nitrogen. The reaction product is detected during the reaction, and heating is stopped when the product and ethanol reach a certain mutual solubility ratio (mutual solubility ratio of 2-6).

[0027] Step 2: A water separator is installed in the four-necked flask, an appropriate amount of water is added to the water separator, and a small amount of water-containing solvent is added dropwise on the water surface. A condensate water device is installed in the water separator. Add anhydride containing a benzene ring and water-containing solvent, and heat to 180-200°C for reaction. After 2h, the molecular weight polydispersity coefficient of the polycondensate is monitored, and heating is stopped when the standard is met. Cool down and take the material to obtain the polycondensate.

[0028] The use of a water separator and a water-containing solvent is to extract the water produced in the reaction, accelerate the reaction to product formation, and improve the conversion rate. The water-containing solvent is not specifically limited.

[0029] In the present application, in the preparation process S1 of the polycondensate, the detection method of the mutual solubility ratio of the reaction product and ethanol is as follows: take a certain volume of reaction product, titrate with ethanol, and stop titration when the titration is completely soluble.

[0030] Mutual solubility ratio = titration volume of ethanol / volume of reaction product.

[0031] The application can realize the control of the polydispersity index of the final condensation polymer, and further control the molecular structure of the condensation polymer by controlling the mutual solubility ratio of the reaction product of the unsaturated fatty acid and the small-molecule polyol and the ethanol in the condensation polymer preparation process.

[0032] According to another aspect of the application, a molded tray is also provided, which is prepared by using the adhesive composition described above.

[0033] In some alternative embodiments, the preparation method of the molded tray comprises the following steps: mixing the adhesive composition with the wood crushed material, placing in a mold, and hot-pressing.

[0034] In some alternative embodiments, the amount of the adhesive composition accounts for 1%-10% of the total mass of the adhesive composition and the wood crushed material;

[0035] And / or, the moisture content of the wood crushed material is 5%-20%.

[0036] In some alternative embodiments, the temperature of the hot-pressing is 120-200℃, the pressure is 15-25MPa, and the pressure holding time is 50-180s.

[0037] In the application, on the one hand, the condensation polymer takes the polyester formed by the acid anhydride containing benzene ring and the polyol as the main chain, and the unsaturated fatty acid and part of the hydroxyl group as the side chain, which constitutes a macromolecular soft structure. During hot-pressing, part of the macromolecules can be cured by themselves, and the hydroxyl group on part of the macromolecules is cured with isocyanate to form a polyurethane structure, which is combined with the polyurea structure cured by isocyanate and water, to form a cross-linked network system combining rigidity and softness, which greatly improves the flexibility of the molded tray while ensuring the strength. On the other hand, by controlling the polydispersity index of the condensation polymer to be 1.5-4.0, the molecular weight distribution is ensured to be neither too concentrated nor too dispersed, so that the condensation polymer has a multiple molecular structure. During the molding process of the molded tray, the low-molecular-weight condensation polymer fills the pores of the wood crushed material, and the high-molecular-weight condensation polymer cures and bonds between the wood crushed materials, so that the toughness of the molded tray is improved under good bonding strength.

[0038] In the application, isocyanate is used as the main component of the adhesive, the condensation polymer is used as the toughening agent, and the diluent is used to reduce the viscosity of the whole system, which is beneficial to subsequent atomization and sizing.

[0039] In the application, the polydispersity index d of the condensation polymer is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), which can be determined by the gel chromatography method known in the industry.

[0040] Specifically, the method for determining the polydispersity index of the polycondensate in the present application is as follows: using a gel chromatograph, a tetrahydrofuran solution (1.5 mg / ml) of the polycondensate is injected into a high-pressure pump and sent into a chromatographic column at a flow rate of 1 ml / min for separation, and the flow time and flow volume are collected by the detector of the instrument to obtain a sample spectrum. The peak area of the polycondensate is integrated by the spectrum and a correction curve, and the Mw and Mn of the polycondensate are calculated, and the polydispersity index d of the molecular weight is calculated by the following formula:

[0041] d = Mw / Mn;

[0042] Specifically, in the present application, the method for preparing the molded tray can be as follows:

[0043] (1) atomization glue mixing: under stirring, the adhesive composition provided by the present application is sprayed by atomization on wood crushed material with a certain water content;

[0044] (2) spraying release agent: the release agent is uniformly sprayed on the mold by atomization spraying;

[0045] (3) hot pressing: after the raw material mixed with glue by atomization in step (1) is placed on the mold and leveled, the raw material is hot pressed under high temperature and high pressure using a press.

[0046] In the present application, the wood crushed material is conventionally obtained by crushing and pulverizing waste plywood, waste solid wood, straw, peanut shells, cotton rods, waste bamboo and the like.

[0047] In the present application, the wood crushed material can be obtained by crushing with a crusher having a screen hole of 10-20 mm.

[0048] The technical solution of the present application has the following advantages:

[0049] The adhesive composition provided by the present application increases the softness of the overall cured product segment by introducing a polycondensate with a specific composition and a polydispersity index, improves the toughness of the overall molded tray, is beneficial to the stability of the tray during operation, and significantly improves the bending strength of the overall molded tray compared with the molded tray without using the polycondensate, reduces the brittle fracture during use, and prolongs the service life of the molded tray.

[0050] Additional aspects and advantages of the present application will be partially given in the following description, partially will become apparent from the following description, or will be understood by practicing the present application. DETAILED DESCRIPTION

[0051] The following examples are provided to further illustrate certain embodiments of the application and are not intended to limit the scope of the application. The examples provided are not exhaustive of all embodiments of the application. Any product, process, or method not expressly excluded or otherwise limiting the scope of the application is deemed to be covered by the application. Any product, process, or method that was known or available at the time of filing of this application but not prior to the effective filing date of this application is considered to be prior art.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise required by context, singular terms shall include pluralities and vice versa.

[0053] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Those skilled in the art will recognize that the embodiments described herein can be combined with one another.

[0054] "Ranges" disclosed herein are defined by both a lower and an upper limit, a given range is defined by selecting a lower limit and an upper limit, the selected lower limit and upper limit define the boundaries of a particular range. Ranges defined by the endpoints can or can not include the endpoints, and can be combined into other ranges by any arbitrary increments, i.e., any lower limit can be combined with any upper limit to form a range. In the present disclosure, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing all the individual real numbers that fall within the range of a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between 0 and 5 have been listed herein, "0-5" is merely a shorthand way of listing all the numbers in that range. Also, when it is stated that a parameter is an integer ≥2, it is equivalent to disclose that the parameter can be, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0055] In the description of the embodiments of the present application, the term "and / or" is merely used to describe associated objects, and can represent the following three meanings: A and / or B can represent that there is only A, or only B, or both A and B.

[0056] In the description of the embodiments of the present application, the term "at least one" refers to one or more than one (including two).

[0057] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0058] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0059] The sources of some of the raw materials involved in the following examples and comparative examples are as follows:

[0060] Wood shreds: waste plywood and waste solid wood, purchased from Anhui Aidesen Environmental Protection Technology Co., Ltd.

[0061] Isocyanate I: PMDI, WANNATE CW20, Wanhua Chemical;

[0062] Isocyanate II: Modified PMDI, WANNATE 9131FC, Wanhua Chemical;

[0063] Isocyanate III: WANNATE HDI, Wanhua Chemical;

[0064] Release agent: silicone oil type, KC201G3, Wanhua Chemical;

[0065] Phthalic anhydride: 99%, INNOCHEM;

[0066] Terephthalic anhydride: 95%, source leaf;

[0067] Trimeric tricarboxylic anhydride: 99%, source leaf;

[0068] Pyromellitic dianhydride: 99%, source leaf;

[0069] Maleic anhydride: 99%, INNOCHEM;

[0070] Lithium hydroxide: 99%, Chinese medicine;

[0071] Sodium hydroxide: 99%, Chinese medicine;

[0072] Potassium hydroxide: 99%, Chinese medicine;

[0073] Xylene: 99%, Chinese medicine;

[0074] Tung oil: 98%, source leaf;

[0075] Castor oil: 99%, China pharmaceutical;

[0076] Palmitic acid: 99%, source leaf;

[0077] Soybean oil: 95%, Hisens;

[0078] Ethylene glycol: 99%, China pharmaceutical;

[0079] Diethylene glycol: 99%, China pharmaceutical;

[0080] Glycerol: 99%, China pharmaceutical;

[0081] Dichloromethane: 99%, China pharmaceutical;

[0082] Dichloroethane: 99%, China pharmaceutical;

[0083] Ethyl acetate: 99%, China pharmaceutical;

[0084] Tray mold: 1.14m x 1.14m x 0.126m, Jiangsu Zhucheng;

[0085] The application will be described below with reference to specific examples, it should be noted that these examples are merely descriptive, and do not limit the application in any way.

[0086] Example 1

[0087] The present embodiment provides an adhesive composition, its composition and preparation method are as follows:

[0088] The raw materials of the condensation polymer include: benzene ring containing anhydride: phthalic anhydride 370g; Unsaturated fatty acid: tung oil 400g; Small molecule polyol: ethylene glycol 230g; Basic catalyst: lithium hydroxide 1g; The general procedure of the preparation process of the condensation polymer is as follows:

[0089] S1, in the nitrogen protection atmosphere, the unsaturated fatty acid and the small molecule polyol are reacted under the catalysis of the basic catalyst, the reaction temperature is 220℃, and the reaction is stopped after the mutual solubility ratio of the product and ethanol reaches the standard;

[0090] S2, a water separator is installed in a four-necked flask, 200g of water is added in the water separator, 10ml of dimethylbenzene is added dropwise on the water surface, and a condensate water device is installed in the water separator. Add the formula mass of benzene ring containing anhydride and 45ml of dimethylbenzene, heat to 180℃, and stop the reaction after monitoring that the polydispersity coefficient of the condensation polymer reaches the standard.

[0091] In this embodiment, the mutual solubility ratio of the reaction product in S1 of the condensation polymer synthesis process is controlled to be 2; The molecular weight dispersity coefficient of the condensation polymer in S2 is controlled to be 1.5.

[0092] In this embodiment, the gel permeation chromatograph (Agilent 1290 Infinity II, Agilent Technologies (China) Co., Ltd.) is used to test the polydispersity index of the polycondensate. Specifically, the tetrahydrofuran solution (1.5 mg / ml) of the polycondensate is injected into the high-pressure pump and sent into the chromatographic column at a flow rate of 1 ml / min for separation. The flow time and flow volume are collected by the detector of the instrument to obtain the sample spectrum. The peak area of the polycondensate is integrated by the spectrum and the correction curve to calculate the Mw and Mn of the polycondensate. The polydispersity index d is calculated by the following formula: d = Mw / Mn.

[0093] The adhesive composition provided in this embodiment includes: isocyanate I: 200 g; polycondensate: 500 g; diluent: dichloromethane 300 g.

[0094] This embodiment also provides a preparation method of a wooden molded tray, and the specific steps are as follows:

[0095] (1) Atomization glue mixing: under the stirring state, 0.72 kg of the adhesive composition is sprayed on the wooden crushed material with 17.28 kg and 20% water content by atomization spraying;

[0096] (2) Spraying release agent: 10 g of release agent is uniformly sprayed on the mold by atomization spraying;

[0097] (3) Hot pressing: after the raw material of step (1) is placed on the mold and leveled, the press is used to hot press at a hot pressing temperature of 130°C, a hot pressing pressure of 17 Mpa and a hot pressing time of 150 s.

[0098] Example 2

[0099] This embodiment provides an adhesive composition, and its composition and preparation method are as follows: the raw materials of the polycondensate include: phenyl-containing anhydride: phthalic anhydride 400 g; unsaturated fatty acid: castor oil 300 g; small molecule polyol: diethylene glycol 300 g; basic catalyst: sodium hydroxide 5 g;

[0100] The polycondensate is prepared according to the method of Example 1, and the difference is that the mutual solubility ratio of the reaction product to ethanol in step S1 is 6, and the polydispersity index of the polycondensate obtained in step S2 is 4.

[0101] The adhesive composition provided in this embodiment includes: isocyanate II: 700 g; polycondensate: 200 g; diluent: dichloroethane 100 g.

[0102] This embodiment also provides a preparation method of a wooden molded tray, and the specific steps are as follows:

[0103] (1) Atomization and glue mixing: 0.54 kg of the adhesive composition is sprayed by atomization on 17.46 kg of wood powder with 15% moisture content under stirring;

[0104] (2) Spraying of release agent: 10 g of release agent is uniformly sprayed on the mold by atomization;

[0105] (3) Hot pressing: the material of step (1) is placed on the mold after being atomized and mixed with glue, and then hot pressing is performed at a hot pressing temperature of 120°C, a hot pressing pressure of 19 MPa, and a hot pressing time of 120 s.

[0106] Example 3

[0107] The adhesive composition provided in this example includes: isocyanate III: 350 g; polycondensate: 350 g; diluent: ethyl acetate 300 g.

[0108] The polycondensate is prepared according to the method of Example 1, with the difference that the mutual solubility ratio of the reaction product to ethanol in step S1 is 3, and the polydispersity coefficient of the polycondensate obtained in step S2 is 2.

[0109] The adhesive composition provided in this example includes: isocyanate III: 350 g; polycondensate: 350 g; diluent: ethyl acetate 300 g.

[0110] This example also provides a method for preparing a wooden molded tray, and the specific steps are as follows:

[0111] (1) Atomization and glue mixing: 0.54 kg of the adhesive composition is sprayed by atomization on 17.46 kg of wood powder with 15% moisture content under stirring;

[0112] (2) Spraying of release agent: 10 g of release agent is uniformly sprayed on the mold by atomization;

[0113] (3) Hot pressing: the material of step (1) is placed on the mold after being atomized and mixed with glue, and then hot pressing is performed at a hot pressing temperature of 120°C, a hot pressing pressure of 19 MPa, and a hot pressing time of 120 s.

[0114] Example 4

[0115] The adhesive composition provided in this example includes: isocyanate III: 350 g; polycondensate: 350 g; diluent: ethyl acetate 300 g.

[0116] The polycondensate was prepared according to the method of Example 1, except that the mutual solubility ratio of the reaction product to ethanol in Step S1 was controlled to be 4, and the polydispersity index of the polycondensate obtained in Step S2 was 2.5.

[0117] The adhesive composition provided in this example includes: isocyanate II: 400 g; polycondensate: 200 g; diluent: chlorobenzene 400 g.

[0118] This example also provides a method for preparing a wooden molded pallet, and the specific steps are as follows:

[0119] (1) Atomization glue mixing: under the stirring state, 0.9 kg of adhesive composition is sprayed by atomization on 17.1 kg of wood crushing material with 12% moisture content;

[0120] (2) Spraying release agent: 10 g of release agent is uniformly sprayed on the mold using atomization spraying;

[0121] (3) Hot pressing: after the raw material of step (1) is placed on the mold and leveled, the press is used to hot press at a hot pressing temperature of 200°C, a hot pressing pressure of 21 MPa, and a hot pressing time of 50 s.

[0122] Example 5

[0123] This example provides an adhesive composition, and its composition and preparation method are as follows: the raw materials of the polycondensate include: benzene ring-containing anhydride: pyromellitic dianhydride 200 g; unsaturated fatty acid: castor oil 500 g; small molecule polyol: diethylene glycol 300 g; basic catalyst: lithium hydroxide 2 g;

[0124] The polycondensate was prepared according to the method of Example 1, except that the mutual solubility ratio of the reaction product to ethanol in Step S1 was controlled to be 5, and the polydispersity index of the polycondensate obtained in Step S2 was 3.3.

[0125] The adhesive composition provided in this example includes: isocyanate I: 550 g; polycondensate: 260 g; diluent: dichloromethane 190 g.

[0126] This example also provides a method for preparing a wooden molded pallet, and the specific steps are as follows:

[0127] (1) Atomization glue mixing: under the stirring state, 0.54 kg of adhesive composition is sprayed by atomization on 17.46 kg of wood crushing material with 20% moisture content;

[0128] (2) Spraying release agent: 10 g of release agent is uniformly sprayed on the mold using atomization spraying;

[0129] (3) Hot-pressing: The material of step (1) was placed on the mold, and after being leveled, the material was hot-pressed at a hot-pressing temperature of 150°C, a hot-pressing pressure of 22 MPa, and a hot-pressing time of 170 s.

[0130] Example 6

[0131] The adhesive composition provided in this example includes: isocyanate II: 620 g; polycondensate: 100 g; diluent: dichloromethane 280 g.

[0132] The polycondensate was prepared according to the method of Example 1, except that the mutual solubility ratio of the reaction product to ethanol in step 1 was controlled to be 3, and the polydispersity index of the obtained polycondensate in step 2 was controlled to be 1.8.

[0133] The adhesive composition provided in this example includes: isocyanate II: 620 g; polycondensate: 100 g; diluent: dichloromethane 280 g.

[0134] Wooden mold pressing tray preparation process:

[0135] (1) Atomization mixing: 0.18 kg of the adhesive composition was sprayed by atomization on the wooden crushed material with a water content of 17.82 kg and 13% under stirring;

[0136] (2) Spraying release agent: 10 g of release agent was uniformly sprayed on the mold using atomization spraying;

[0137] (3) Hot-pressing: The material of step (1) was placed on the mold, and after being leveled, the material was hot-pressed at a hot-pressing temperature of 170°C, a hot-pressing pressure of 25 MPa, and a hot-pressing time of 180 s.

[0138] Example 7

[0139] The adhesive composition provided in this example includes: isocyanate II: 620 g; polycondensate: 100 g; diluent: dichloromethane 280 g.

[0140] The polycondensate was prepared according to the method of Example 1, except that the mutual solubility ratio of the reaction product to ethanol in step 1 was controlled to be 4, and the polydispersity index of the obtained polycondensate in step 2 was controlled to be 3.7.

[0141] The adhesive composition provided in the embodiment includes: isocyanate III: 450 g; polycondensate: 310 g; diluent: dichloromethane 200 g, dichloroethane 40 g.

[0142] The embodiment also provides a preparation method of the wooden molded tray, and the specific steps are as follows:

[0143] (1) atomization glue mixing: 1.8 kg of the adhesive composition is sprayed on the wooden crushed material with 16.2 kg and 9% water content by atomization spraying in a stirring state;

[0144] (2) spraying release agent: 10 g of the release agent is uniformly sprayed on the mold by atomization spraying;

[0145] (3) hot pressing: the raw material mixed with glue by atomization in step (1) is placed on the mold, and after being leveled, the raw material is hot pressed by using a press at a hot pressing temperature of 190 ℃, a hot pressing pressure of 18 Mpa and a hot pressing time of 120 s.

[0146] Example 8

[0147] The embodiment provides an adhesive composition and a molded tray, and the difference compared with example 3 is that the preparation parameters of the polycondensate are different, and the specific parameters are as follows: the reaction temperature of S1 is 220 ℃; and the reaction temperature of S2 is 180 ℃.

[0148] Example 9

[0149] The embodiment provides an adhesive composition and a molded tray, and the difference compared with example 3 is that the preparation parameters of the polycondensate are different, and the specific parameters are as follows: the reaction temperature of S1 is 200 ℃; and the reaction temperature of S2 is 200 ℃.

[0150] Comparative example 1

[0151] The comparative example provides an adhesive composition and a molded tray, and the difference compared with example 2 is that the adhesive composition includes: isocyanate: 0 g; polycondensate: 800 g; diluent: dichloromethane 200 g.

[0152] Comparative example 2

[0153] The comparative example provides an adhesive composition and a preparation method of a wooden tray, and the difference compared with comparative example 2 is that the adhesive composition provided in the comparative example includes: isocyanate I: 800 g; diluent: dichloromethane 200 g; and polycondensate: 0 g.

[0154] Comparative example 3

[0155] The comparative example provides a method for preparing an adhesive composition and a wooden pallet, which is different from example 2 in that the mutual solubility ratio during the synthesis of the polycondensate is 1.5, and the molecular weight polydispersity index of the polycondensate is 1.3.

[0156] Comparative example 4

[0157] The comparative example provides a method for preparing an adhesive composition and a wooden pallet, which is different from example 2 in that the mutual solubility ratio during the synthesis of the polycondensate is 7, and the molecular weight polydispersity index of the polycondensate is 6.

[0158] Comparative example 5

[0159] The comparative example provides a method for preparing an adhesive composition and a wooden pallet, which is different from example 2 in that the benzenic anhydride in the polycondensate is replaced by maleic anhydride.

[0160] Comparative example 6

[0161] The comparative example provides a method for preparing an adhesive composition and a wooden pallet, which is different from example 2 in that the unsaturated fatty acid in the polycondensate is replaced by palmitic acid.

[0162] Test example

[0163] The molded pallets provided by each example and comparative example are tested, and the specific test method is as follows:

[0164] A pallet mechanical tester (PN-CT50KE, Hangzhou Pinxiang Technology Co., Ltd.) is used to test the bending strength, fork lifting performance and board surface concentrated load of the pallet;

[0165] The bending strength performance is tested according to the standard GB / T 4995-2014 “Performance requirements and test selection of general pallets for intermodal transport” 8.1 test 1: bending test. The fork lifting performance is tested according to the standard GB / T 4995-2014 “Performance requirements and test selection of general pallets for intermodal transport” 8.2 test 2: fork lifting test. The board surface concentrated load performance is tested according to the standard GB / T 4995-2014 “Performance requirements and test selection of general pallets for intermodal transport” 8.4 test 4: stacking test.

[0166] The specific test results are shown in the following table:

[0167] Table 1

[0168]

[0169]

[0170] From the bending strength of the examples 1-9 and the comparative example 2, it can be seen that the bending strength of the wood-molded tray can be obviously improved by using the polycondensate, and the lowest can be improved by 20%. It is illustrated that the toughness of the tray can be obviously improved by the cooperation of the polycondensate with the molecular weight polydispersity coefficient and the isocyanate. The bending performance of the tray is relatively poor without using the isocyanate (comparative example 1) or without using the polycondensate.

[0171] From the examples 1-9 and the comparative examples 3, 4, it can be seen that the bending strength of the wood-molded tray cannot be obviously improved by using the polydispersity coefficient lower than 1.5 or higher than 6, which is mainly due to the unreasonable molecular weight distribution, and the crosslinking system cannot meet the performance requirement of the wood-molded tray.

[0172] From the examples 1-9 and the comparative example 5, it can be seen that the bending strength of the tray cannot be obviously improved by using the polycondensate synthesized by the non-benzene ring anhydride, and the possible reason is that the benzene ring structure is lack of compatibility with the isocyanate structure, and the synergistic effect is not played.

[0173] From the examples 1-9 and the comparative example 6, it can be seen that the bending strength of the tray is reduced by using the polycondensate synthesized by the saturated fatty acid, and the possible reason is that the lack of unsaturated double bond affects the curing speed of the polycondensate.

[0174] Obviously, the above examples are only examples for clearly illustrating, and are not limitation to the embodiments. Other different forms of changes or variations can be made by the ordinary skilled in the art on the basis of the above description. All the embodiments do not need to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An adhesive composition, characterized in that, It includes the following components in weight percentage: isocyanate 20%-70%; condensate 10%-50%; diluent 10%-40%; The condensation polymer is a condensation polymer of an acid anhydride containing a benzene ring, an unsaturated fatty acid, and a small molecule polyol, and the molecular weight polydispersity index of the condensation polymer is 1.5-4.

0.

2. The adhesive composition according to claim 1, characterized in that, It includes the following components by weight percentage: isocyanate 40%-60%; condensate 20%-30%; diluent 20%-40%.

3. The adhesive composition according to claim 1 or 2, characterized in that, The total mass of the benzene-containing acid anhydride, unsaturated fatty acid, and small molecule polyol includes 20%-60% benzene-containing acid anhydride, 25%-50% unsaturated fatty acid, and 10%-30% small molecule polyol. Optionally, it includes 40%-60% of benzene ring-containing acid anhydrides, 30%-45% of unsaturated fatty acids, and 10%-30% of small molecule polyols.

4. The adhesive composition according to any one of claims 1-3, characterized in that, The method for preparing the condensation polymer includes the following steps: S1, In a protective atmosphere, unsaturated fatty acids and small molecule polyols are reacted under the catalysis of an alkaline catalyst at a reaction temperature of 180-220℃, and the reaction is stopped when the miscibility ratio of the product to ethanol is 2-6. S2, add benzene-containing acid anhydride and aqueous solvent and react at 180-200℃, monitor the molecular weight and polydispersity index of the condensation polymer, and stop the reaction after the target is reached.

5. The adhesive composition according to claim 4, characterized in that, In S1, the alkaline catalyst includes at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; And / or, based on the total mass of the unsaturated fatty acids, small molecule polyols and benzene ring-containing acid anhydrides, the amount of the alkaline catalyst is 0.1%-0.5%; And / or, stop the reaction when the product is miscible with ethanol at a ratio of 3-5; And / or, in S2, the aqueous solvent includes at least one of xylene, benzene, toluene, xylene, and cyclohexane.

6. The adhesive composition according to claim 1 or 2, characterized in that, The benzene ring-containing acid anhydride includes at least one of phthalic anhydride, terephthalic anhydride, trimellitic anhydride, and pyromellitic dianhydride. And / or, the unsaturated fatty acids include at least one of linseed oil, tung oil, castor oil, tung oil, soybean oil, coconut oil, and palm oil; And / or, the molecular weight of the small molecule polyol is 10-200 and the functionality is 2-4; optionally, the small molecule polyol includes at least one of ethylene glycol, 1,2-propanediol, 1,4-butanediol, diethylene glycol, and glycerol. And / or, the isocyanate includes at least one of polymethylene polyphenyl polyisocyanate and / or its derivatives; And / or, the diluent includes at least one of dichloromethane, dichloroethane, ethyl acetate, and chlorobenzene.

7. A molded tray, characterized in that, It is prepared using the adhesive composition according to any one of claims 1-6.

8. The molded tray according to claim 7, characterized in that, The preparation method includes the following steps: mixing the adhesive composition with wood pulverizer, placing it in a mold, and hot pressing it into shape.

9. The molded tray according to claim 8, characterized in that, The amount of adhesive composition used is 1%-10% based on the total mass of the adhesive composition and the wood shreds; And / or, the moisture content of the wood shreds is 5%-20%.

10. The molded tray according to claim 8 or 9, characterized in that, The hot pressing temperature is 120-200℃, the pressure is 15-25MPa, and the holding time is 50-180s.

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