PUR (Polyurethane) hot melt adhesive based on biological material and preparation method of PUR hot melt adhesive

Abstract

The invention discloses a PUR hot melt adhesive based on a biological material and a preparation method thereof, and belongs to the technical field of preparation of hot melt adhesives with special functions. The hot melt adhesive comprises the following components in percentage by mass: 60-85% of bio-based polyester polyol, 10-30% of polyisocyanate, 5-15% of biocompatible tackifying resin, 0.01-0.05% of a catalyst and 0.1-0.5% of a natural antioxidant, the bio-based polyester polyol is prepared from ricinoleic acid and succinic anhydride through an esterification reaction, and the hydroxyl value is 40-60 mgKOH / g. Through the synergistic effect of the ricinoleic acid-based polyester polyol with a specific structure and the hydrogenated rosin ester, the bio-based content is increased, the opening time is prolonged, the thermal decomposition temperature is increased, the itaconate copolymer effectively blocks the reaction of isocyanate and water, the moisture curing speed is increased, the bubble rate is reduced, and the curing time is shortened. The industrial problem that the performance of the bio-based PUR adhesive is degraded in a high-humidity environment is solved.

Description

Technical Field

[0001] This invention relates to a biomaterial-based PUR hot melt adhesive and its preparation method, belonging to the field of special functional hot melt adhesive preparation technology. Background Technology

[0002] Traditional polyurethane reactive hot melt adhesives in current industrial production still heavily rely on petrochemical products for their raw material composition. Specifically, they mainly include polyether polyols as the base polymer, aromatic isocyanates that perform cross-linking reactions, and petroleum resins used to enhance viscosity—all derived from non-renewable petroleum resources. Limited by this raw material system, the proportion of bio-based components in these hot melt adhesives is generally low, typically less than 30%. This means that the vast majority of components in their material structure are difficult to degrade rapidly in the natural environment. Actual data shows that the complete degradation cycle of these products under natural conditions often exceeds 200 years. Such a long degradation process not only causes a serious environmental burden but may also lead to long-term ecological problems. Simultaneously, during the processing and manufacturing of PUR hot melt adhesives, the volatile components in the raw materials inevitably release benzene-based volatiles. These substances not only pose a potential threat to the health of production workers but may also cause air pollution in the workshop, failing to meet the environmental standards of modern green production. To improve this situation, existing technologies have begun to explore the introduction of bio-based materials as alternatives. Soybean oil polyols are a commonly used bio-based raw material, aiming to increase the bio-based content of products, reduce dependence on petroleum resources, and improve degradation performance. However, in practical applications, the use of these bio-based materials faces significant technical bottlenecks: on the one hand, biomaterials such as soybean oil polyols generally suffer from uneven molecular weight distribution, with a molecular weight distribution index typically greater than 2.5. This imbalance in molecular structure directly affects the overall stability of the material. On the other hand, these biomaterials often have excessively high branching, resulting in overly complex molecular chain structures. These two factors combined lead to significant performance defects in the improved PUR hot melt adhesive products. Specifically, the open time is drastically shortened, typically less than 90 seconds, which greatly reduces the adjustment window during actual operation, making rapid bonding operations on the production line difficult. Simultaneously, the initial tack strength of the product also decreases significantly, generally below 1.5 N / mm². 2This makes it difficult to meet the initial bonding performance requirements in many scenarios. More seriously, in high humidity environments, i.e., when the relative humidity exceeds 80%, the bonding strength of these modified products can decrease by more than 40%. This drastic fluctuation in performance makes them unsuitable for fields with high environmental adaptability requirements, especially in the two key areas of food packaging and medical devices. Food packaging needs to maintain its sealing performance for a long time to ensure food freshness, while medical devices have extremely high standards for bonding stability and safety. This strength decay problem under high humidity directly limits its application possibilities and cannot meet the stringent usage requirements of these fields. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides: 1. A biomaterial-based PUR hot melt adhesive, comprising the following components by weight percentage:

[0004] Bio-based polyester polyols 60-85%,

[0005] Polyisocyanates 10-30%,

[0006] Biocompatible tackifying resin 5-15%,

[0007] Catalyst 0.01-0.05%,

[0008] Natural antioxidants 0.1-0.5%,

[0009] The bio-based polyester polyol is prepared by esterification of ricinoleic acid and succinic anhydride, and has a hydroxyl value of 40-60 mg KOH / g.

[0010] Preferably, the preparation of the bio-based polyester polyol comprises the following steps:

[0011] (a) Mix ricinoleic acid and succinic anhydride in a mass ratio of 6.5:3.5 to 7:3;

[0012] (b) Add 0.5-1.5% of tetrabutyl titanate catalyst by total mass of the mixture;

[0013] (c) Stir the reaction at 115-125℃ under nitrogen protection for 3.5-4.5 hours;

[0014] (d) The reaction product was subjected to vacuum distillation to remove unreacted monomers, and the hydroxyl value was controlled to be 40-60 mg KOH / g.

[0015] Preferably, the polyisocyanate is at least one of 4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI).

[0016] Preferably, the biocompatible tackifying resin is at least one of hydrogenated rosin glycerol ester, methyl abirate, or itaconic acid ester copolymer.

[0017] Preferably, the catalyst is at least one of dibutyltin dilaurate, stannous octoate, or a bio-enzyme catalyst.

[0018] Preferably, the natural antioxidant is at least one of rosemary extract, tocopherol, or tea polyphenols.

[0019] The present invention also provides a method for preparing the above-mentioned PUR hot melt adhesive, comprising the following steps:

[0020] (1) Dehydrate the bio-based polyester polyol by heating under nitrogen protection;

[0021] (2) After cooling, add the biocompatible thickening resin and stir;

[0022] (3) Add polyisocyanate and heat to react;

[0023] (4) Add catalyst and natural antioxidant, and vacuum degas for 0.5 hours;

[0024] (5) Cool to room temperature and discharge.

[0025] Preferably, the dehydration temperature in step (1) is 100-110℃ and the dehydration time is 1-3h;

[0026] Preferably, the cooling in step (2) is to cool to 70-80°C, and the stirring time is 20-50 minutes.

[0027] Preferably, the heating reaction in step (3) is carried out at 85±2℃ for 3-4 hours, wherein the isocyanate index (NCO / OH molar ratio) is controlled at 1.05-1.15.

[0028] Preferably, the moisture content of the polyol after dehydration is ≤0.03wt%.

[0029] The present invention also applies the above-mentioned PUR hot melt adhesive to the bonding of wood panels, sealing of paper packaging materials, or perfect binding of books and periodicals.

[0030] The beneficial effects of this invention are:

[0031] This invention utilizes the synergistic effect of a specific structured castor oil-based polyester polyol (hydroxyl value 40-60 mg KOH / g) and hydrogenated rosin ester to increase the bio-based content to 72-85% while extending the open time to 150-180 seconds and achieving an initial tack strength of 2.8-3.5 N / mm. 2The catalyst / antioxidant system raises the thermal decomposition temperature to over 280℃, and the strength retention rate exceeds 90% after 1000 hours of humid heat aging at 60℃. The itaconic acid ester copolymer effectively blocks the reaction between isocyanate and water, increasing the wet curing speed by 40% and reducing the bubble rate to below 0.5%, solving the industry problem of performance degradation of bio-based PUR adhesives in high humidity environments. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used in the following examples are all purchased from commercial channels.

[0035] Example 1

[0036] 65g of ricinoleic acid and 35g of succinic anhydride were esterified at 120℃ for 4 hours to obtain a polyol with a hydroxyl value of 45mgKOH / g. 80g of this polyol was dehydrated at 105℃ for 2 hours under nitrogen protection until the water content was no higher than 0.02%. The mixture was cooled to 75℃, and 12g of hydrogenated rosin glycerol ester was added and stirred until dissolved. 25g of MDI (NCO / OH = 1.08) was added, and the reaction was carried out at 85℃ for 3 hours. 0.03g of dibutyltin dilaurate and 0.3g of rosemary extract were added, and the mixture was degassed under vacuum for 0.5 hours before being discharged.

[0037] Example 2

[0038] Polyols with a hydroxyl value of 55 mg KOH / g (mass ratio of ricinoleic acid to succinic anhydride) were prepared according to the method in Example 1.

[0039] =7:3). Take 70g of polyol, dehydrate it, add 10g of methyl abirate to dissolve it, add 28g of IPDI (NCO / OH = 1.12), and then follow the same procedure as in Example 1. Add 0.02g of stannous octoate and 0.4g of tocopherol.

[0040] Example 3

[0041] A polyol with a hydroxyl value of 50 mg KOH / g was prepared according to the method in Example 1. 75 g of the dehydrated polyol was dissolved in 15 g of itaconic acid ester copolymer, followed by the addition of 22 g of HDI (NCO / OH = 1.05), and then proceeded as in Example 1. 0.04 g of a bio-enzyme catalyst and 0.2 g of tea polyphenols were added.

[0042] Comparative Example 1 (Conventional Petroleum-based)

[0043] The preparation process was the same as in Example 1, using 80g of polytetrahydrofuran polyol (PTMEG), 15g of petroleum resin, 30g of MDI (NCO / OH = 1.10), 0.03g of catalyst, and 0.3g of antioxidant BHT.

[0044] Comparative Example 2 (insufficient bio-based content)

[0045] In Example 1, the bio-based polyol was replaced with 40g, and an additional 40g of petroleum-based polyester polyol was added, while the other components remained unchanged.

[0046] Comparative Example 3 (lacking biocompatible thickener)

[0047] In Example 1, hydrogenated rosin glycerol ester was removed from the formulation, the amount of polyol was increased to 92g, and the rest remained unchanged.

[0048] The products obtained from all embodiments and comparative examples were tested according to the methods described below, and the results are shown in Table 1.

[0049] Detection method:

[0050] Bio-based content: According to ASTM D6866 standard, 50 mg of sample was pyrolyzed at 900℃ and then separated by GC. The modern carbon content was calculated by the 14C / 12C ratio. The instrument used was an Elementarvario PYROcube coupled with a GC-MS.

[0051] Isoprime100 isotopic spectrum.

[0052] Opening time: GB / T4851-2014, apply molten adhesive (120℃) to pine wood chips (100×25mm), immediately stack them with another substrate, apply pressure with a 1kg weight, and record the maximum time interval for adjusting the position.

[0053] Bond strength: ISO4587:2003. Birch wood test pieces (100×25×5mm) with a bonded area of ​​12.5×25mm were cured at 23℃ / 50%RH for 7 days, then stretched at a speed of 10mm / min. The average value of 5 test pieces was taken.

[0054] Damp heat aging: GB / T16995-1997, place the bonded specimens in a constant temperature and humidity chamber at 60℃ / 95%RH, and test the strength retention rate after 1000 hours.

[0055] VOC detection: GB33372-2020, take 5g of sample and heat at 120℃ for 30min, adsorb the released gas using a Tenax tube, analyze by TD-GC / MS, and integrate the peak areas of C6-C16 compounds.

[0056] Table 1 Test Results

[0057]

[0058] Firstly, compared to the traditional petroleum-based PUR adhesive shown in Example 1, although it possesses high adhesive strength, its bio-based content is only 12%, and it suffers from defects such as a high VOC release of 285 μg / g and a low strength retention rate of only 65% ​​under damp heat aging. The core innovation of this invention lies in using a novel system composed of a specific hydroxyl-value polyester polyol synthesized from castor oil acid and succinic anhydride, synergistically formulated with a biocompatible tackifier. Examples 1-3 verify that this combination achieves a bio-based content exceeding 78-83%, while simultaneously realizing multiple performance breakthroughs: the phenolic hydroxyl groups of hydrogenated rosin glycerol ester form a hydrogen bond network with the isocyanate, thus... The open time was extended to 175 seconds, an improvement of 113% compared to 82 seconds in Comparative Example 3 when this component was missing. The itaconic acid ester copolymer traps ambient moisture through carboxyl groups, reducing the moisture curing bubble rate to 0.3% and accelerating the curing rate by 40%. More importantly, this invention overturns the technical prejudice that bio-based content above 60% inevitably leads to a decrease in mechanical properties. Experiments show that the strength of Comparative Example 2 decreased by 29% when the bio-based content was 45%. This invention, by controlling the hydroxyl value of the polyol and the proportion of rigid segments of succinic anhydride, achieves an initial tack strength of 3.2 N / mm while maintaining a high bio-based content. 2 The above results show that after 1000 hours of damp heat aging at 60℃ / 95%RH, the strength retention rate exceeded 90%, while VOC emissions decreased to 38μg / g and benzene compounds were undetectable. This indicates that the synergistic effect of the components enabled Example 1 to achieve a peel strength of 8.5N / mm, while Comparative Example 3, lacking the tackifier, plummeted to 5.3N / mm. The critical threshold study of bio-based content confirmed that Example 2 still met the usage requirements at a content of 78%, but when the content of Comparative Example 2 decreased to 45%, the biodegradation rate deteriorated from 98% to 65%, confirming 60% as the performance inflection point. In summary, the above scheme, through a specific bio-based component system and precise process control, such as the dosage of tetrabutyl titanate catalyst in polyol synthesis at 0.5-1.5% and a reaction temperature window of 115-125℃, achieves 85% bio-based content and 98% biodegradation rate while maintaining excellent adhesive performance, fundamentally solving the industry's technical bottleneck of the difficulty in reconciling environmental protection and high performance.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0060] The present invention and its embodiments have been described above, and such description is not restrictive. In summary, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A PUR hot melt adhesive based on biomaterials, characterized in that: It contains the following components by mass percentage: Bio-based polyester polyols 60-85%, Polyisocyanates 10-30%, Biocompatible tackifying resin 5-15%, Catalyst 0.01-0.05%, Natural antioxidants 0.1-0.5%, The bio-based polyester polyol is prepared by esterification of ricinoleic acid and succinic anhydride, and has a hydroxyl value of 40-60 mg KOH / g.

2. The PUR hot melt adhesive according to claim 1, characterized in that: The polyisocyanate is at least one of 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, or isophorone diisocyanate.

3. The PUR hot melt adhesive according to claim 1, characterized in that: The biocompatible tackifying resin is at least one of hydrogenated rosin glycerol ester, methyl abirate, or itaconic acid ester copolymer.

4. The PUR hot melt adhesive according to claim 1, characterized in that: The catalyst is at least one of dibutyltin dilaurate, stannous octoate, or a bio-enzyme catalyst.

5. The PUR hot melt adhesive according to claim 1, characterized in that: The natural antioxidant is at least one of rosemary extract, tocopherol, or tea polyphenols.

6. A method for preparing the PUR hot melt adhesive according to any one of claims 1-5, characterized in that: Includes the following steps: (1) Dehydrate the bio-based polyester polyol by heating under nitrogen protection; (2) After cooling, add the biocompatible thickening resin and stir; (3) Add polyisocyanate and heat to react; (4) Add catalyst and natural antioxidant, and vacuum degas for 0.5 hours; (5) Cool to room temperature and discharge.

7. The preparation method according to claim 6, characterized in that: The dehydration temperature in step (1) is 100-110℃ and the dehydration time is 1-3h.

8. The preparation method according to claim 6, characterized in that: The cooling process described in step (2) involves cooling the temperature to 70-80℃ and stirring for 20-50 minutes.

9. The preparation method according to claim 6, characterized in that: The heating reaction described in step (3) is carried out at 85±2℃ for 3-4 hours, wherein the isocyanate index is 1.05-1.

15.

10. An application of the PUR hot melt adhesive as described in any one of claims 1-5, characterized in that: Used for bonding wood panels, sealing paper packaging materials, or perfect binding of books and periodicals.

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