A hyperbranched polyamide modifier, modified melamine-formaldehyde resin and its applications

Abstract

This invention discloses a hyperbranched polyamide modifier, a modified melamine-formaldehyde resin, and their applications, belonging to the technical field of melamine-formaldehyde resin modification. The modifier is prepared from tetraethylenepentamine, ethylenediaminetetraacetic acid (EDTA), a catalyst, and water; the molar ratio of tetraethylenepentamine to EDTA is 1:(0.3-1); the amount of catalyst is 0.5-1.5 wt% of the total mass of tetraethylenepentamine and EDTA. The hyperbranched polyamide modifier prepared by this invention is compatible with melamine-formaldehyde resin, improving toughness and appropriately reducing formaldehyde release.

Description

Technical Field

[0001] This invention relates to the field of melamine-formaldehyde resin modification technology, and in particular to a hyperbranched polyamide modifier, modified melamine-formaldehyde resin, and their applications. Background Technology

[0002] Melamine-formaldehyde resin, also known as melamine resin, is a linear or branched macromolecular compound obtained by the condensation of melamine and formaldehyde, belonging to thermosetting resins. In the wood processing industry, plain paper or printed decorative paper is impregnated with melamine-formaldehyde resin and dried to a certain extent to obtain a film paper with a certain resin content. This film paper is then bonded to a particleboard substrate using a hot-pressing process, which can beautify the substrate's appearance, improve its physical properties, and increase the value of the particleboard. However, melamine-formaldehyde resin has a high cross-linking density and contains a large number of rigid triazine ring structures, making the cured resin brittle and prone to cracking under stress, thus limiting its industrial application. Research has shown that by adding toughening modifiers to melamine-formaldehyde resin through blending or reaction, the distance between the triazine rings can be extended to achieve a toughening effect, improving its impact resistance and fatigue resistance without compromising the original dimensional stability of the melamine-formaldehyde resin. There are many toughening methods for melamine-formaldehyde resin, but not all of them are applicable to melamine-formaldehyde resin for impregnation. The toughening modification of the resin for impregnation should be adapted to the production conditions of the film paper. Attention should also be paid to the viscosity of the modified resin before curing (the viscosity of the resin for impregnating film paper should preferably be below 20s), impregnation, and pre-curing degree.

[0003] Modification of melamine-formaldehyde resin is usually achieved by adding modifiers (toughening agents) during the preparation of melamine-formaldehyde resin to participate in a chemical reaction, such as CN107522830A, CN102875755A, and CN117683194A. However, the preparation process is complex. Alternatively, a new type of modifier can be prepared and then added to the melamine-formaldehyde resin system for direct on-site mixing and use, such as CN118126310A. However, the shelf life of the modifier is relatively short, and the long molecular chains of high molecular weight polymers have strong intermolecular forces, resulting in high viscosity, poor flowability, and difficulty in adapting to the production conditions of adhesive film paper. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a hyperbranched polyamide modifier, a modified melamine-formaldehyde resin, and its applications. The amino-terminated hyperbranched polyamide modifier prepared by this invention exhibits an irregular three-dimensional spherical structure with large internal voids, allowing it to be blended and compatible with melamine-formaldehyde resin, thereby enhancing toughness to a certain extent and appropriately reducing formaldehyde release.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] On one hand, the present invention provides a hyperbranched polyamide modifier, which is prepared from tetraethylenepentamine, ethylenediaminetetraacetic acid, a catalyst and water; the molar ratio of tetraethylenepentamine to ethylenediaminetetraacetic acid is 1:(0.3-1); the amount of catalyst is 0.5-1.5 wt% of the total mass of tetraethylenepentamine and ethylenediaminetetraacetic acid.

[0007] Furthermore, the catalyst is one or a mixture of several of p-toluenesulfonic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide, and 4-dimethylaminopyridine.

[0008] Preferably, the catalyst is 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

[0009] The present invention also provides a method for preparing the above-mentioned hyperbranched polyamide modifier, comprising: uniformly mixing tetraethylenepentamine, ethylenediaminetetraacetic acid and water, heating, then adding a catalyst, reacting for a period of time and then carrying out a dehydration reaction, and then placing it in a water bath to cool to room temperature.

[0010] Furthermore, the above preparation method specifically includes:

[0011] 1) Mix tetraethylenepentamine, ethylenediaminetetraacetic acid and water evenly, and heat to 135-145℃;

[0012] 2) Add catalyst and react for 0.5-1 hour;

[0013] 3) Heat to 155-165℃ and react for 0.5-1 hour;

[0014] 4) Heat to 170℃ and allow the dehydration reaction to proceed for 0.5-1 hour;

[0015] 5) Cool down to 90-110℃, add water to adjust the solid content of the modifier to 20-60%, and then place it in a water bath to quickly cool to room temperature.

[0016] Preferably, in step 1), the amount of water used is 15-20 wt% of the total mass of tetraethylenepentamine, ethylenediaminetetraacetic acid and water.

[0017] On the other hand, the present invention provides a modified melamine-formaldehyde resin, which is composed of the following components by mass percentage: 97.95 wt% melamine-formaldehyde resin, 2 wt% of the above-mentioned modifier, and 0.05 wt% curing agent.

[0018] The above-mentioned method for preparing modified melamine-formaldehyde resin involves mixing the melamine-formaldehyde resin, the above-mentioned modifier, and the curing agent evenly in a high-speed dispersion homogenizer.

[0019] In another aspect, the present invention also provides the application of the above-mentioned modified melamine-formaldehyde resin in impregnated paper decorative panels.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses a hyperbranched polyamide modifier prepared by reacting tetraethylenepentamine and ethylenediaminetetraacetic acid. This modifier possesses a unique three-dimensional spherical molecular structure, which is less prone to entanglement and exhibits weak intermolecular interactions, allowing for relatively free molecular movement and resulting in lower viscosity. Furthermore, it is compatible with melamine-formaldehyde resin, enhancing toughness to a certain extent and appropriately reducing formaldehyde release, thus producing impregnated paper-faced plywood with better mechanical properties. The modifier prepared in this invention is safe and simple to prepare, has a high yield, relatively low cost, and is easily scalable for industrial production. Attached Figure Description

[0022] Figure 1 The infrared spectrum of the hyperbranched polyamide modifier prepared in Example 1 of this invention. Detailed Implementation

[0023] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0024] Unless otherwise specified, all materials and reagents used in this invention are commercially available. Specifically, the melamine-formaldehyde resin (solid content ≥50%) and curing agent used below are from Hangzhou Tianyuan Chengda Decoration Materials Co., Ltd. The tetraethylenepentamine purity is 95%, and the ethylenediaminetetraacetic acid purity is 99.5%; the catalyst is 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

[0025] This invention provides a hyperbranched polyamide modifier, a modified melamine-formaldehyde resin, and their applications, with specific embodiments as follows.

[0026] Example 1

[0027] A method for preparing a hyperbranched polyamide modifier, comprising:

[0028] 1) In a 2L flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet and outlet, tetraethylenepentamine, ethylenediaminetetraacetic acid and water are mixed evenly under a nitrogen atmosphere and heated to 140°C.

[0029] 2) Add the catalyst 1-ethyl-(3-dimethylaminopropyl)carbodiimide and react for 0.5 hours;

[0030] 3) Heat to 160℃ and react for 0.5 hours;

[0031] 4) Heat to 170℃ and dehydrate for 0.5 hours;

[0032] 5) Cool down to 90-110℃, add 200g of water, mix well, and then place in a water bath to quickly cool to room temperature;

[0033] 6) Adjust the solid content of the modifier to 50%.

[0034] The infrared spectrum of the prepared modifier is shown below. Figure 1 As shown, the prepared modifier has amide characteristic peaks, proving that the hyperbranched polyamide modifier was successfully prepared.

[0035] A modified melamine-formaldehyde resin is composed of the following components by mass percentage: 97.95 wt% melamine-formaldehyde resin, 2 wt% of the above-mentioned modifier, and 0.05 wt% curing agent; the three components are mixed uniformly using a high-speed dispersion homogenizer (4000 r / min, 5 min).

[0036] Examples 2-4

[0037] In Examples 2-4, the amounts of each raw material used in the modifier are shown in Table 1, and the other conditions are the same as in Example 1.

[0038] The dosage of each component of the modified melamine-formaldehyde resin is shown in Table 2.

[0039] Table 1

[0040]

[0041] Table 2

[0042]

[0043] To further illustrate the beneficial effects of the present invention, due to space limitations, only Example 1 is used as an example to construct a comparative case as follows.

[0044] Comparative Example 1

[0045] An unmodified melamine-formaldehyde resin: 500 grams of melamine-formaldehyde resin and 2.5 grams of curing agent. The melamine-formaldehyde resin and curing agent are mixed evenly using a high-speed dispersion homogenizer (4000 r / min, 5 min).

[0046] Comparative Example 2

[0047] In this comparative example, tetraethylenepentamine was replaced with an equimolar amount of diethylenetriamine, and the other conditions were the same as in Example 1.

[0048] Comparative Example 3

[0049] In this comparative example, tetraethylenepentamine was replaced with an equimolar amount of triethylenetetramine, and the other conditions were the same as in Example 1.

[0050] Comparative Example 4

[0051] In this comparative example, ethylenediaminetetraacetic acid was replaced with an equimolar amount of sebacic acid, and the other conditions were the same as in Example 1.

[0052] Comparative Example 5

[0053] In this comparative example, ethylenediaminetetraacetic acid was replaced with an equimolar amount of 1,2,3-propanetricarboxylic acid, and the other conditions were the same as in Example 1.

[0054] Comparative Example 6

[0055] In step 1) of this comparative example, the amount of tetraethylenepentamine used was 189.3g, ethylenediaminetetraacetic acid was 584.49g and water was 158g. In step 2), the amount of catalyst used was 3.9g, and the other conditions were the same as in Example 1.

[0056] Comparative Example 7

[0057] In this comparative example, ethylenediaminetetraacetic acid was replaced with an equimolar amount of citric acid, and the other conditions were the same as in Example 1.

[0058] Comparative Example 8

[0059] In this comparative example, ethylenediaminetetraacetic acid (EDTA) was replaced with an equimolar mixture of EDTA and citric acid (EDTA to citric acid in a molar ratio of 1:1, and the sum of their molar amounts was equal to that of EDTA in Example 1), and the other conditions were the same as in Example 1.

[0060] Comparative Example 9

[0061] In this comparative example, the amount of modifier used was 8%, and the other conditions were the same as in Example 1.

[0062] Comparative Example 10

[0063] In this comparative example, the amount of modifier used was 8%, and the other conditions were the same as in comparative example 3.

[0064] According to GB / T 14074-2017 "Test Methods for Adhesives and Resins for Wood Industry", the appearance, solid content, viscosity and free formaldehyde of the melamine-formaldehyde resins in Examples 1-4 and Comparative Examples 1-10 were tested, and the test results are shown in Table 3.

[0065] Table 3

[0066]

[0067] As shown in the table above, the modified melamine-formaldehyde resin prepared by this invention is a light yellow transparent liquid with a viscosity of 14.42-15.65s and a free formaldehyde content between 0.18-0.44%. The viscosity is low, which can meet the production conditions of impregnated paper, and the free formaldehyde content is low. The viscosity of pure melamine-formaldehyde resin (Comparative Example 1) is lower, but its formaldehyde content is relatively high, which is not environmentally friendly. Replacing tetraethylenepentamine with diethylenetriamine (Comparative Example 2) or triethylenetetraamine (Comparative Example 3) slightly increases the viscosity of the resulting resin, and the free formaldehyde content is more than 65% higher than in Example 1. Replacing ethylenediaminetetraacetic acid with sebacic acid (Comparative Example 4) increases the viscosity by 61.5% and the free formaldehyde content by 39%. Replacing ethylenediaminetetraacetic acid with 1,2,3-propanetricarboxylic acid (Comparative Example 5) does not significantly increase the viscosity, but the free formaldehyde content is higher. Changing the amount of modifier in the formulation (Comparative Example 6) increases both the viscosity and the free formaldehyde content. Replacing all or part of ethylenediaminetetraacetic acid with citric acid (Comparative Examples 7-8) does not significantly differ from the examples in terms of viscosity and free formaldehyde content. Increasing the amount of modifier (Comparative Examples 9-10) leads to a significant increase in the viscosity of the prepared resin.

[0068] Impregnated films were prepared using the melamine-formaldehyde resins of Examples 1-6 and Comparative Examples 1-10 of the present invention, respectively. The base paper was impregnated with the resin adhesive of the examples and comparative examples, with an impregnation amount of 110-170%. The impregnated base paper was dried at a temperature of 120°C to obtain the impregnated films of the examples and comparative examples.

[0069] Impregnated paper-faced plywood was prepared using the impregnated paper in the embodiments and comparative examples of the present invention, as detailed below:

[0070] 1) Plywood: Moisture content 8-12%, bonding strength 0.9 MPa;

[0071] 2) Hot pressing: Temperature 120℃, pressure 1.0MPa, time 6min.

[0072] The physical and chemical properties of impregnated paper-faced plywood and blockboard were tested according to GB / T 34722-2017 "Impregnated Paper-faced Plywood and Blockboard". The test results are shown in Tables 4-5.

[0073] Table 4

[0074]

[0075] Test results show that the impregnated paper prepared using the modified melamine-formaldehyde resin of this invention exhibits significantly improved toughness, with a cracking grade of 5, tensile strength of 68.49 N, and elongation at break of 15.56%. Abrasion resistance is reduced, and surface hardness and scratch resistance are improved. No cracks, blistering, discoloration, or wrinkling were observed during thermal cycling. The impregnated paper prepared using the modified melamine-formaldehyde resin of this invention conforms to the specifications of GB / T 34722-2017 "Impregnated Paper-Faced Plywood and Blockboard".

[0076] Table 5

[0077]

[0078] As shown in Table 5, the surface of pure melamine-formaldehyde resin (Comparative Example 1) exhibits cracking, blistering, discoloration, and wrinkling during thermal cycling, and its tensile strength and elongation at break are significantly reduced. Replacing tetraethylenepentamine with diethylenetriamine (Comparative Example 2) or triethylenetetraamine (Comparative Example 3) increases the abrasion value and significantly reduces tensile strength and elongation at break. Replacing ethylenediaminetetraacetic acid with sebacic acid (Comparative Example 4) does not differ much from the examples in terms of performance, but the viscosity is higher, making it difficult to impregnate evenly. Replacing ethylenediaminetetraacetic acid with 1,2,3-propanetricarboxylic acid (Comparative Example 5) significantly reduces the cracking grade, tensile strength, and elongation at break. The plywood prepared in Comparative Examples 6-10 all exhibit some poor performance characteristics.

[0079] In summary, the hyperbranched polyamide modifier prepared by the reaction of tetraethylenepentamine and ethylenediaminetetraacetic acid in this invention has a low viscosity and is compatible with melamine-formaldehyde resin, thereby enhancing toughness and appropriately reducing formaldehyde release to a certain extent, resulting in better mechanical properties of the prepared impregnated paper-faced plywood. The modifier of this invention is safe and simple to prepare, has a high yield, and relatively low cost, making it easy to achieve industrial production.

[0080] The above description is a preferred embodiment of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A modified melamine-formaldehyde resin, characterized in that, It is composed of the following components by weight percentage: melamine-formaldehyde resin 94.9-99.45 wt%, hyperbranched polyamide modifier 0.5-5 wt%, curing agent 0.05-0.1 wt%; The above-mentioned hyperbranched polyamide modifier is prepared from tetraethylenepentamine, ethylenediaminetetraacetic acid, catalyst and water; the molar ratio of tetraethylenepentamine to ethylenediaminetetraacetic acid is 1:(0.3-1); the amount of catalyst is 0.5-1.5 wt% of the total mass of tetraethylenepentamine and ethylenediaminetetraacetic acid.

2. The modified melamine-formaldehyde resin according to claim 1, characterized in that, It is composed of the following components by weight percentage: 97.95 wt% melamine-formaldehyde resin, 2 wt% hyperbranched polyamide modifier, and 0.05 wt% curing agent.

3. The modified melamine-formaldehyde resin according to claim 1, characterized in that, The catalyst is one or a mixture of several of p-toluenesulfonic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide, and 4-dimethylaminopyridine.

4. The modified melamine-formaldehyde resin according to claim 3, characterized in that, The catalyst is 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

5. The modified melamine-formaldehyde resin according to claim 4, characterized in that, The preparation method of the hyperbranched polyamide modifier includes: uniformly mixing tetraethylenepentamine, ethylenediaminetetraacetic acid and water, heating, then adding a catalyst, reacting for a period of time and then carrying out a dehydration reaction, and then placing it in a water bath to cool to room temperature.

6. The modified melamine-formaldehyde resin according to claim 5, characterized in that, The preparation method of the hyperbranched polyamide modifier specifically includes: 1) Mix tetraethylenepentamine, ethylenediaminetetraacetic acid and water evenly, and heat to 135-145℃; 2) Add catalyst and react for 0.5-1 hour; 3) Heat to 155-165℃ and react for 0.5-1 hour; 4) Heat to 170℃ and allow the dehydration reaction to proceed for 0.5-1 hour; 5) Cool down to 90-110℃, add water to adjust the solid content of the modifier to 20-60%, and then place it in a water bath to quickly cool to room temperature.

7. The modified melamine-formaldehyde resin according to claim 6, characterized in that, In step 1), the amount of water used is 15-20 wt% of the total mass of tetraethylenepentamine, ethylenediaminetetraacetic acid and water.

8. The method for preparing the modified melamine-formaldehyde resin according to any one of claims 1-7, characterized in that, Simply mix the melamine-formaldehyde resin, hyperbranched polyamide modifier, and curing agent evenly in a high-speed dispersion homogenizer.

9. The use of the modified melamine-formaldehyde resin according to any one of claims 1-7 in impregnated paper decorative panels.

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