An optically transparent pressure-sensitive adhesive composition with body temperature-driven viscosity transition and its preparation method

Abstract

This invention relates to the field of temperature-responsive optically transparent pressure-sensitive adhesives, specifically disclosing an optically transparent pressure-sensitive adhesive composition and its preparation method that can be driven by body temperature to achieve a change in viscosity. The optically transparent pressure-sensitive adhesive composition that can be driven by body temperature to achieve a change in viscosity comprises the following components in parts by weight: 10-30 parts of a photocurable polypropylene glycol-based polyurethane prepolymer, 10-30 parts of a low-polarity acrylate monomer, 10-30 parts of a high-polarity acrylate monomer, 20-40 parts of a long-side-chain acrylate monomer, 0.5-2 parts of a photoinitiator, and 2-5 parts of an antioxidant. The initial tack of the pressure-sensitive adhesive composition of this invention can be controlled with temperature changes, and exhibits significant changes within the human body temperature range, making it particularly suitable for load substrates of wearable devices.

Description

Technical Field

[0001] This invention relates to the field of temperature-responsive optically transparent pressure-sensitive adhesives, specifically disclosing an optically transparent pressure-sensitive adhesive composition and its preparation method that can be driven by body temperature to change viscosity. Background Technology

[0002] With the increasing demand for wearable electronics and stimulus-responsive adhesives, temperature-responsive optically transparent pressure-sensitive adhesives are attracting attention from both academia and industry.

[0003] For optically transparent pressure-sensitive adhesives, CN201610355301.5, "UV-curable pressure-sensitive composition and adhesive," discloses a UV-curable pressure-sensitive composition and adhesive. This UV-curable pressure-sensitive composition includes oligomers, reactive diluents, and photoinitiators. The weight ratio of reactive diluent to oligomers is 40:60 to 60:40, and the photoinitiator accounts for 1 to 5% of the composition by weight. Furthermore, by weight, the oligomers include 20 to 40 parts of polyolefin acrylate and 4 to 30 parts of polyurethane acrylate. This UV-curable pressure-sensitive composition does not cause pollution from solvent evaporation during use; moreover, by controlling the weight ratio of the reactive diluent (as a monomer) to the oligomer between 40:60 and 60:40, the adhesive performance of the pressure-sensitive adhesive is greatly improved; furthermore, by using polyolefin acrylate as the oligomer component, the olefin functional groups therein give the pressure-sensitive adhesive formed by the UV-curable pressure-sensitive composition strong weather resistance, thereby giving it high light transmittance.

[0004] For temperature-responsive pressure-sensitive adhesives, PCT / US2012 / 047274, "Heat-debondable adhesive article and methods of making and using the same," discloses a heat-debondable adhesive article having two opposing sides. The article comprises a shape memory polymer sheet in its temporary strain shape, including a plurality of slits, a first adhesive on one opposing side of the polymer sheet, and a second adhesive on the other opposing side of the polymer sheet. The article can be debonded by heating it to a temperature equal to or higher than the transition temperature of the shape memory polymer sheet. The shape memory polymer sheet comprises epoxy resin, thermosetting polyurethane, acrylate, styrene-based polymer, crosslinked olefin, or crosslinked ring-opening metathesis polymer.

[0005] However, existing temperature-responsive optically transparent pressure-sensitive adhesives have practical application problems such as volatile solvent residues, high driving temperatures, and inability to be driven in wearable body temperature environments. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention aims to provide an optically transparent pressure-sensitive adhesive composition that can be driven by body temperature to change its viscosity.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned optically transparent pressure-sensitive adhesive composition that can undergo a temperature-driven viscosity change.

[0008] Another object of the present invention is to provide applications of the above-described composition.

[0009] The objective of this invention is achieved through the following solution: an optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition, comprising the following components in parts by weight:

[0010] 10-30 parts of photocurable polypropylene glycol-based polyurethane prepolymer, 10-30 parts of low-polarity acrylate monomer, 10-30 parts of high-polarity acrylate monomer, 20-40 parts of long-side-chain acrylate monomer, 0.5-2 parts of photoinitiator, and 2-5 parts of antioxidant.

[0011] The mechanism of this invention is as follows: by adopting the above technical solution, the interaction between polyurethane and acrylate monomers is changed by using photocurable polypropylene glycol-type polyurethane prepolymer, and the crystallization behavior of long side chain acrylate monomers is adjusted by combining low polarity acrylate monomers and high polarity acrylates. The resulting pressure-sensitive adhesive composition has a temperature-driven viscosity transition and exhibits a significant viscosity change near human body temperature. It is particularly suitable for applications such as the load substrate of wearable devices that require temperature-responsive viscosity.

[0012] Based on the above scheme, the light-curable polypropylene glycol-type polyurethane prepolymer raw material includes polyurethane prepolymers containing partially isocyanate groups and partially (meth)acrylate groups, and small molecule alcohols.

[0013] Furthermore, the small molecule alcohols mentioned include one of methanol, ethanol, isopropanol, and isooctanol.

[0014] Furthermore, the polyurethane prepolymer containing partially isocyanate-terminated and partially (meth)acrylate-terminated groups includes hydroxy (meth)acrylate, diisocyanate, and polyether diol; wherein,

[0015] Preferably, the hydroxy(meth)acrylate comprises one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate;

[0016] Preferably, the diisocyanate comprises one of the following: aliphatic diisocyanate such as isophorone diisocyanate, dicyclohexane 4,4'-diisocyanate, m-phenylenedimethyl isocyanate, aromatic diisocyanate such as toluene diisocyanate, and diphenylmethane diisocyanate, and the isocyanate index (R value) is between 1.5 and 2.0;

[0017] Preferably, the polyether diol is a polypropylene glycol diol with a molecular weight of 1000-4000.

[0018] In this invention, the method for preparing the polyurethane prepolymer containing partially isocyanate-terminated and partially (meth)acrylate-terminated groups includes the following steps:

[0019] Polypropylene glycol diol was dehydrated at 110 °C for 2 h, then cooled to 70 °C, and diisocyanate was added. The mixture was then reacted under organotin catalysis for 3-6 h to obtain an isocyanate-terminated polyurethane prepolymer. After naturally cooling to 60 °C, hydroxy (meth)acrylate was added and reacted for 1-2 h to obtain a polyurethane prepolymer containing both isocyanate and acrylate-terminated groups.

[0020] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups, along with small molecule alcohols, are further reacted at 60°C for 1-2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0021] In one specific implementation, the average acrylate content of the photocurable polypropylene glycol-based polyurethane prepolymer is 0.8 or 2.0.

[0022] In one specific feasible embodiment, the photocurable polypropylene glycol-based polyurethane prepolymer has a weight-average molecular weight of 5-10 kg mol. -1 The dispersion is between 1.5 and 2.0.

[0023] In one specific implementation, the photoinitiator includes one of TPO, TPO-L, CB-1, and photoinitiator 184.

[0024] In one specific feasible implementation, the antioxidant is one of 2,6-di-tert-butyl-p-cresol, hydroquinone, and antioxidant 1010.

[0025] The present invention also provides a method for preparing an optically transparent pressure-sensitive adhesive composition with a viscosity change induced by body temperature, comprising the following steps:

[0026] At 40-50℃, the long-side-chain acrylate monomers are fully melted, and the antioxidant, photoinitiator, photocurable polypropylene glycol-type polyurethane prepolymer, low-polarity acrylate monomers, and high-polarity acrylate monomers are stirred and degassed to obtain a uniform and transparent pressure-sensitive adhesive composition.

[0027] The present invention also provides the application of an optically transparent pressure-sensitive adhesive composition with a body temperature-driven viscosity transition in a load matrix for wearable devices.

[0028] The present invention also provides a photocurable polypropylene glycol-based polyurethane for use in optically transparent pressure-sensitive adhesive compositions with body temperature-driven viscosity transitions, and a method for preparing the same.

[0029] The beneficial technical effects of this invention are:

[0030] By utilizing photocurable polypropylene glycol-based polyurethane prepolymers to modify the interaction between polyurethane and acrylate monomers, and by combining low-polarity acrylate monomers and high-polarity acrylate monomers to synergistically adjust the crystallization behavior of long-side-chain acrylate monomers, a pressure-sensitive adhesive composition was obtained that exhibits a temperature-driven viscous transition and shows a significant viscous change near human body temperature. This composition is particularly suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0031] Polypropylene glycol diol is dehydrated and reacted with different diisocyanates under the action of a catalyst to obtain isocyanate-terminated polyurethane prepolymers. Hydroxy(meth)acrylate monomers are further added to react and obtain polyurethane prepolymers with partial isocyanate and partial acrylate terminates. Finally, the polyurethane prepolymers with partial isocyanate and partial (meth)acrylate terminates are reacted with small molecule alcohols to obtain stable photocurable polypropylene glycol-type polyurethane prepolymers.

[0032] The preparation process in this invention does not require the use of volatile organic solvents, which meets the current trend of green and environmentally friendly preparation. Attached Figure Description

[0033] Figure 1 The GPC curve of the photocurable polypropylene glycol-based polyurethane prepolymer prepared in Example 1;

[0034] Figure 2 The GPC curve of the photocurable polypropylene glycol-based polyurethane prepolymer prepared in Example 2;

[0035] Figure 3 The GPC curve of the photocurable polypropylene glycol-based polyurethane prepolymer prepared in Example 3;

[0036] Figure 4 The GPC curve of the photocurable polypropylene glycol-based polyurethane prepolymer prepared in Example 4;

[0037] Figure 5 GPC curves of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in Comparative Example 1.

[0038] Figure 6 GPC curves of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in Comparative Example 2.

[0039] Figure 7 GPC curves of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in Comparative Example 3.

[0040] Figure 8 GPC curves of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in Comparative Example 4.

[0041] Figures 1 to 8 They have similar molecular weights and dispersities. Detailed Implementation

[0042] All raw materials used in the examples are commercially available.

[0043] The preferred low-polarity acrylate monomer is isooctyl acrylate;

[0044] The highly polar acrylate is preferably hydroxyethyl acrylate;

[0045] The long-chain acrylate monomer is preferably a combination of lauryl acrylate and octadecyl acrylate;

[0046] The small molecule alcohols mentioned include one of methanol, ethanol, isopropanol, and isooctanol, with methanol being preferred;

[0047] The hydroxy(meth)acrylate comprises one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate, preferably hydroxyethyl acrylate;

[0048] The diisocyanate comprises one of the following: aliphatic diisocyanates such as isophorone diisocyanate, dicyclohexane 4,4'-diisocyanate, m-phenylenediamine diisocyanate, aromatic diisocyanates such as toluene diisocyanate, and diphenylmethane diisocyanate, preferably isophorone diisocyanate, dicyclohexane 4,4'-diisocyanate, m-phenylenediamine diisocyanate, and diphenylmethane diisocyanate;

[0049] The polyether diol is a polypropylene glycol diol with a molecular weight of 1000-4000, preferably polypropylene glycol 1000;

[0050] The photoinitiators include TPO, TPO-L (a highly efficient liquid universal UV photoinitiator with good solubility), CB-1, and photoinitiator 184 (also known as HCPK). The present invention preferably uses TPO (the main chemical component is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxychloride, which has a wide absorption spectrum, with an effective absorption peak of 350-400 nm, absorbing up to about 420 nm).

[0051] The antioxidant is one of 2,6-di-tert-butyl-p-cresol, hydroquinone, and antioxidant 1010, preferably 2,6-di-tert-butyl-p-cresol.

[0052] Example 1

[0053] An optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition is prepared according to the following steps:

[0054] 1) Raw material preparation: Weigh the raw materials according to the formula, including a light-curable polypropylene glycol-based polyurethane prepolymer, prepared according to the following steps:

[0055] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.05 wt% of organotin catalyst was added. Subsequently, 0.16 mol of m-phenylenedimethyl isocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. The temperature was then further lowered to 60°C, and 0.048 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0056] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0057] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 4.4 kg mol. -1 The weight-average molecular weight is 7.5 kg mol. -1 The dispersion is 1.7, and its GPC curve is as follows: Figure 1 As shown.

[0058] 2) At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in step 1), 1 g of TPO and 5 g of 2,6-di-tert-butyl-p-cresol were added to a mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0059] The resulting transparent pressure-sensitive adhesive had an initial tack of 0 at 23°C and an initial tack of 18 at 37°C, with a transmittance of 90% (see Table 1), demonstrating the characteristics of body temperature-driven tack change and optical transparency.

[0060] It exhibits a significant change in viscosity near human body temperature, making it suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0061] Example 2

[0062] This embodiment provides an optically transparent pressure-sensitive adhesive composition with a viscosity change driven by body temperature. Other raw materials and proportions are the same as in Example 1, except that the preparation of the photocurable polypropylene glycol-based polyurethane prepolymer is slightly different, wherein:

[0063] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, which, compared to step 1) of Example 1, does not have a reaction step with a small molecule alcohol and differs in the amount of hydroxyethyl acrylate added, was prepared according to the following method:

[0064] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.05 wt% of organotin catalyst was added. Then, 0.16 mol of m-phenylenedimethyl isocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.12 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0065] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 4.6 kg mol. -1 The weight-average molecular weight is 7.5 kg mol. -1 The dispersion is 1.6, and the GPC curve is as follows: Figure 2 .

[0066] 2) An optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition is prepared according to the following steps:

[0067] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form a mixed acrylate monomer. Subsequently, 20 g of the photocurable polypropylene glycol-type polyurethane prepolymer obtained in Preparation Example 2, 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to a mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0068] The resulting transparent pressure-sensitive adhesive had an initial tack of 0 at 23°C and an initial tack of 11 at 37°C, with a transmittance of 91% (see Table 1), demonstrating the characteristics of body temperature-driven tack change and optical transparency.

[0069] It exhibits a significant change in viscosity near human body temperature, making it suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0070] Example 3

[0071] This embodiment provides an optically transparent pressure-sensitive adhesive composition with a viscosity change driven by body temperature. Other raw materials and proportions are the same as in Example 1, except that the preparation of the photocurable polypropylene glycol-based polyurethane prepolymer is slightly different.

[0072] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, with a different amount of organotin catalyst added than in step 1) of Example 1, was prepared according to the following steps:

[0073] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.01 wt% of organotin catalyst was added. Subsequently, 0.16 mol of diphenylmethane diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. The temperature was then lowered to 60 °C, and 0.048 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0074] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0075] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 4.5 kg mol. -1 The weight-average molecular weight is 7.3 kg mol. -1 The dispersion is 1.6, and the GPC curve is as follows: Figure 3 .

[0076] 2) An optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition is prepared according to the following steps:

[0077] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in step 1), 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to the mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0078] The resulting transparent pressure-sensitive adhesive had an initial tack of 0 at 23°C and an initial tack of 22 at 37°C, with a transmittance of 91% (see Table 1), demonstrating the characteristics of body temperature-driven tack change and optical transparency.

[0079] It exhibits a significant change in viscosity near human body temperature, making it suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0080] Example 4

[0081] This embodiment provides an optically transparent pressure-sensitive adhesive composition with a viscosity change driven by body temperature. Other raw materials and proportions are the same as in Example 1, except...

[0082] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, with a different amount of organotin catalyst added compared to Example 2, and without a reaction step with small molecule alcohols, was prepared according to the following steps:

[0083] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.01 wt% of organotin catalyst was added. Subsequently, 0.16 mol of diphenylmethane diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Then, the temperature was lowered to 60°C, and 0.12 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0084] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 4.6 kg mol. -1 The weight-average molecular weight is 7.4 kg mol. -1 The dispersion is 1.6, and the GPC curve is as follows: Figure 4 .

[0085] 2) An optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition, prepared according to the following steps:

[0086] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the prepared photocurable polypropylene glycol polyurethane prepolymer, 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to the mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0087] The resulting transparent pressure-sensitive adhesive had an initial tack of 0 at 23°C and an initial tack of 9 at 37°C, with a transmittance of 91% (see Table 1), demonstrating the characteristics of body temperature-driven tack change and optical transparency.

[0088] It exhibits a significant change in viscosity near human body temperature, making it suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0089] Comparative Example 1

[0090] This comparative example provides a transparent pressure-sensitive adhesive composition. Other raw materials and proportions are the same as in Example 1, except that...

[0091] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, which differs from the diisocyanate raw material in step 1) of Example 1, is isophorone diisocyanate, and is prepared according to the following steps:

[0092] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60°C, and 0.048 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0093] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0094] The obtained photocurable polypropylene glycol-based polyurethane prepolymer had a number-average molecular weight of 4.3 kg mol. -1The weight-average molecular weight is 6.7 kg mol. -1 The dispersion is 1.6, and the GPC curve is as follows: Figure 5 .

[0095] 2) The transparent pressure-sensitive adhesive composition is prepared according to the following steps:

[0096] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the photocurable polypropylene glycol-type polyurethane prepolymer prepared in step 1), 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to a mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0097] The resulting transparent pressure-sensitive adhesive has an initial tack of 25 at 23°C and 24 at 37°C, with a transmittance of 92% (see Table 1). It has optical transparency but does not have the property of temperature-driven tack change.

[0098] Comparative Example 2

[0099] This comparative example provides a transparent pressure-sensitive adhesive composition, with other raw materials and proportions the same as in Example 1, except...

[0100] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, with different diisocyanate raw materials (isophorone diisocyanate) and different amounts of hydroxyethyl acrylate added, and without a reaction step with small molecule alcohols, is prepared according to the following steps:

[0101] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.12 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0102] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 3.5 kg mol. -1 The weight-average molecular weight is 6.0 kg mol. -1 The dispersion is 1.7, and the GPC curve is as follows: Figure 6 .

[0103] 2) The transparent pressure-sensitive adhesive composition is prepared according to the following steps:

[0104] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the photocurable polypropylene glycol polyurethane prepolymer prepared in step 1), 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to the mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0105] The resulting transparent pressure-sensitive adhesive has an initial tack of 7 at 23°C and 7 at 37°C, with a transmittance of 92% (see Table 1). It has optical transparency but does not have the property of body temperature-driven tack change and has low tack.

[0106] Comparative Example 3

[0107] This comparative example provides a transparent pressure-sensitive adhesive composition, with other raw materials and proportions the same as in Example 1, except that:

[0108] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, the diisocyanate raw material of which differs from step 1 of Example 1, is dicyclohexane 4,4'-diisocyanate; prepared according to the following steps:

[0109] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.05 wt% of an organotin catalyst was added. 0.16 mol of dicyclohexane 4,4'-diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.048 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0110] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0111] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 5.5 kg mol. -1 The weight-average molecular weight is 9.5 kg mol. -1 The dispersion is 1.7, and the GPC curve is as follows: Figure 7 .

[0112] 2) A transparent pressure-sensitive adhesive composition, prepared according to the following steps:

[0113] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a mixing tank and stirred to remove bubbles. The stirring speed was 300 r / min for 10 min to form mixed acrylate monomers. Subsequently, 20 g of the photocurable polypropylene glycol polyurethane prepolymer prepared in step 1), 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to the mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0114] The resulting transparent pressure-sensitive adhesive has an initial tack of 19 at 23°C and 24 at 37°C, with a transmittance of 92% (see Table 1). It has optical transparency but does not have the property of body temperature-driven tack change and has low tack strength.

[0115] Comparative Example 4

[0116] This comparative example provides a transparent pressure-sensitive adhesive composition, with other raw materials and proportions the same as in Example 1, except that:

[0117] 1) A photocurable polypropylene glycol-based polyurethane prepolymer, the diisocyanate raw material is different from step 1 of Example 1, the amount of hydroxyethyl acrylate added is different and there is no small molecule alcohol reaction step, and it is prepared according to the following steps:

[0118] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.05 wt% of organotin catalyst was added. Subsequently, 0.16 mol of dicyclohexane 4,4'-diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Then, the temperature was lowered to 60°C, and 0.12 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0119] The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 5.1 kg mol. -1 The weight-average molecular weight is 8.3 kg mol. -1 The dispersion is 1.6, and the GPC curve is as follows: Figure 8 .

[0120] 2) A transparent pressure-sensitive adhesive composition and its preparation method, comprising the following steps:

[0121] At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed. Then, 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to the mixing tank and the mixture was stirred and degassed at a speed of 300 r / min for 10 min to form a mixed acrylate monomer. Subsequently, 20 g of the photocurable polypropylene glycol polyurethane prepolymer prepared in step 1), 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to the mixing tank and stirred and degassed to fully mix at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0122] The resulting transparent pressure-sensitive adhesive has an initial tack of 0 at 23°C and an initial tack of 3 at 37°C, with a transmittance of 91% (see Table 1). It exhibits optical transparency, a weak body temperature-driven tack transition, and low tack strength.

[0123] Performance testing

[0124] Adhesion performance test: The transparent pressure-sensitive adhesive compositions in each example and comparative example were coated on a PET film containing silicone oil and cured using a 365 nm LED cold light source. After curing for 2 minutes, the adhesive film was obtained. The initial tack ball number of the adhesive film was tested at different temperatures using the inclined plane rolling ball method. The larger the ball number, the better the adhesion.

[0125] Optical performance testing: The transmittance of the film was measured using a transmittance haze meter.

[0126]

[0127] refer to Figure 1-8 The photocurable polypropylene glycol-based polyurethane prepolymers have similar molecular weights and dispersions, demonstrating a stable synthesis process.

[0128] Referring to Table 1 and the optically transparent pressure-sensitive adhesives in Examples 1-4 and Comparative Examples 1-4, the visible light transmittance in all examples is greater than or equal to 90%, proving that they can be used for optical applications. Compared with the comparative examples, Examples 1-4 all showed more significant changes in initial tack in response to temperature, with Example 3 exhibiting the highest initial tack near body temperature.

[0129] In summary, photocurable polypropylene glycol-based polyurethane prepolymers alter the interaction between polyurethane and acrylate monomers, and by combining low-polarity acrylate monomers and high-polarity acrylate monomers to synergistically adjust the crystallization behavior of long-side-chain acrylate monomers, the resulting pressure-sensitive adhesive composition exhibits a temperature-driven viscous transition and shows a significant viscous change near human body temperature. This makes it particularly suitable for applications requiring temperature-responsive viscosity, such as load substrates for wearable devices.

[0130] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An optically transparent pressure-sensitive adhesive composition with a viscosity change induced by body temperature, characterized in that... It includes the following components in parts by weight: The composition includes 10-30 parts of a photocurable polypropylene glycol-based polyurethane prepolymer, 10-30 parts of low-polarity acrylate monomers, 10-30 parts of high-polarity acrylate monomers, 20-40 parts of long-side-chain acrylate monomers, 0.5-2 parts of a photoinitiator, and 2-5 parts of an antioxidant. The obtained photocurable polypropylene glycol-based polyurethane prepolymer has a number-average molecular weight of 4.4-4.6 kg mol. -1 The weight-average molecular weight is 7.3-7.5 kg mol. -1 The dispersion is 1.7; The low-polarity acrylate monomer is isooctyl acrylate; The highly polar acrylate is hydroxyethyl acrylate; The long-side-chain acrylate monomer is a combination of lauryl acrylate and octadecyl acrylate; The photocurable polypropylene glycol-based polyurethane prepolymer is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.05 wt% organotin catalyst was added. 0.16 mol of m-phenylenedimethyl isocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.048 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups. Alternatively, 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.01 wt% of organotin catalyst was added. 0.16 mol of diphenylmethane diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.048 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups. The polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer; or, The photocurable polypropylene glycol-based polyurethane prepolymer is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70 °C, and 0.05 wt% organotin catalyst was added. Then, 0.16 mol of m-phenylenedimethyl isocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60 °C, and 0.12 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a photocurable polypropylene glycol-based polyurethane prepolymer; or... The photocurable polypropylene glycol-based polyurethane prepolymer is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was lowered to 70°C, and 0.01 wt% of organotin catalyst was added. Then, 0.16 mol of diphenylmethane diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60°C, and 0.12 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

2. The optically transparent pressure-sensitive adhesive composition with body temperature-driven viscosity change according to claim 1, characterized in that... : The photoinitiator includes one of TPO, TPO-L, CB-1, and photoinitiator 184; The antioxidant is one of 2,6-di-tert-butyl-p-cresol, hydroquinone, and antioxidant 1010.

3. A method for preparing an optically transparent pressure-sensitive adhesive composition with body temperature-driven viscosity transition according to claim 1 or 2, characterized in that... The steps include the following: At 40-50℃, the long side-chain acrylate monomers are fully melted and mixed according to the formula amount. Then, low polarity acrylate monomers and high polarity acrylate monomers are added to a mixing tank and mixed and stirred to remove bubbles. The stirring speed is 300r / min and the time is 10min to form mixed acrylate monomers. Subsequently, the photocurable polypropylene glycol-based polyurethane prepolymer, photoinitiator, and antioxidant were added to a mixing tank and stirred to remove bubbles and mix thoroughly. The stirring speed was 100 r / min and the time was 10 min to obtain a transparent pressure-sensitive adhesive composition.

4. The application of an optically transparent pressure-sensitive adhesive composition with body temperature-driven viscosity transition as described in claim 1 or 2 in applications where the load substrate of a wearable device requires temperature-responsive viscosity.

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