Optical transparent pressure-sensitive adhesive composition capable of driving viscosity conversion by body temperature and preparation method of optical transparent pressure-sensitive adhesive composition

Abstract

The invention relates to the technical field of temperature response type optical transparent pressure-sensitive adhesives, and particularly discloses an optical transparent pressure-sensitive adhesive composition capable of driving viscosity conversion by body temperature and a preparation method of the optical transparent pressure-sensitive adhesive composition. The invention discloses an optical transparent pressure-sensitive adhesive composition capable of driving viscosity conversion by body temperature. The optical transparent pressure-sensitive adhesive composition comprises the following components in parts by weight: 10-30 parts of a photocurable polypropylene glycol type 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 anti-aging agent. The initial viscosity of the pressure-sensitive adhesive composition can be regulated and controlled along with temperature change, and the pressure-sensitive adhesive composition has significant change in a human body temperature range, and is especially suitable for a load substrate of a wearable device.

Description

Technical Field

[0001] The invention relates to the technical field of temperature-responsive optically transparent pressure-sensitive adhesives, and specifically discloses an optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature and a preparation method thereof. Background Art

[0002] With the increasing demand for wearable electronic devices and stimuli-responsive adhesives, temperature-responsive optically transparent pressure-sensitive adhesives have attracted attention from both academia and industry.

[0003] For optically transparent pressure-sensitive adhesives, CN201610355301.5 "UV-curable pressure-sensitive composition and pressure-sensitive adhesive" discloses a UV-curable pressure-sensitive composition and pressure-sensitive adhesive. The UV-curable pressure-sensitive composition includes an oligomer, a reactive diluent and a photoinitiator, the weight ratio of the reactive diluent to the oligomer is 40:60 to 60:40, and the weight content of the photoinitiator in the composition is 1 to 5%; and in parts by weight, the oligomer includes: 20 to 40 parts of polyolefin acrylate and 4 to 30 parts of polyurethane acrylate. The UV-curable pressure-sensitive composition will not cause pollution caused by solvent volatilization during use; and the weight ratio of the active diluent as a monomer to the oligomer is controlled between 40:60 and 60:40, so that the bonding performance of the pressure-sensitive adhesive is greatly improved; further, polyolefin acrylate is used as a component of the oligomer, and the olefin functional group therein makes the pressure-sensitive adhesive formed by the UV-curable pressure-sensitive composition have strong weather resistance, thereby making it have a higher light transmittance.

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

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

[0006] In order to solve the above technical problems, the present invention aims to provide an optically transparent pressure-sensitive adhesive composition whose viscosity transition can be driven by body temperature.

[0007] Another object of the present invention is to provide a method for preparing the optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature.

[0008] Another object of the present invention is to provide application of the above composition.

[0009] The object of the present invention is achieved by the following scheme: An optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition at body temperature comprises the following components in parts by weight: 10-30 parts of photocurable polypropylene glycol type 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.

[0010] The mechanism of the present invention is: by adopting the above-mentioned technical scheme, using photocurable polypropylene glycol type polyurethane prepolymer to change the interaction between polyurethane and acrylate monomers, and combining low-polarity acrylate monomers and high-polarity acrylates to synergistically adjust the crystallization behavior of long side chain acrylate monomers, the obtained 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 application scenarios that require temperature-responsive viscosity, such as load substrates of wearable devices.

[0011] On the basis of the above scheme, the photocurable polypropylene glycol type polyurethane prepolymer raw material includes a polyurethane prepolymer containing a part of isocyanate groups and a part of (meth)acrylate groups, and small molecule alcohols.

[0012] Furthermore, the small molecule alcohol includes one of methanol, ethanol, isopropanol and isooctyl alcohol.

[0013] Furthermore, the polyurethane prepolymer containing a portion of isocyanate groups and a portion of (meth)acrylate groups comprises hydroxy (meth)acrylate, diisocyanate, and polyether diol; wherein, Preferably, the hydroxy(meth)acrylate comprises one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate; Preferably, the diisocyanate comprises an aliphatic diisocyanate such as isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, m-xylyl diisocyanate, an aromatic diisocyanate such as toluene diisocyanate, diphenylmethane diisocyanate, and the isocyanate index (R value) is 1.5-2.0; Preferably, the polyether diol is a polypropylene glycol diol having a molecular weight of 1000-4000.

[0014] In the present invention, the preparation method of the polyurethane prepolymer containing part of the isocyanate group-terminated and part of the (meth)acrylate group-terminated comprises the following steps: The polypropylene glycol diol is dehydrated at 110 °C for 2 h, then cooled to 70 °C, and diisocyanate is added and reacted under organic tin catalysis for 3-6 h to obtain an isocyanate group-terminated polyurethane prepolymer; then the temperature is naturally cooled to 60 °C, and hydroxy (meth) acrylate is added and further reacted for 1-2 h to obtain a polyurethane prepolymer containing partly isocyanate group-terminated and partly acrylate group-terminated.

[0015] The polyurethane prepolymer containing part of the isocyanate group-capped and part of the acrylate group-capped and small molecule alcohols are further reacted at 60° C. for 1-2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0016] In a specific embodiment, the average acrylate number of the photocurable polypropylene glycol type polyurethane prepolymer is 0.8 or 2.0. In a specific embodiment, the weight average molecular weight of the photocurable polypropylene glycol type polyurethane prepolymer is 5-10 kg mol -1 The dispersion is between 1.5-2.0.

[0017] In a specific embodiment, the photoinitiator includes one of TPO, TPO-L, CB-1, and photoinitiator 184.

[0018] In a specific embodiment, the antioxidant is one of 2,6-di-tert-butyl-p-cresol, hydroquinone, and antioxidant 1010.

[0019] The present invention also provides a method for preparing an optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature, comprising the following steps: At 40-50° C., the long side chain acrylate monomer is fully melted, and the antioxidant, photoinitiator, photocurable polypropylene glycol type polyurethane prepolymer, low polar acrylate monomer and high polar acrylate monomer are stirred, degassed and fully mixed to obtain a uniform transparent pressure-sensitive adhesive composition.

[0020] The present invention also provides an application of an optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature in a load matrix of a wearable device.

[0021] The present invention also provides a photocurable polypropylene glycol type polyurethane for an optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature and a preparation method thereof.

[0022] The beneficial technical effects of the present invention are: By using photocurable polypropylene glycol-type polyurethane prepolymer to change the interaction between polyurethane and acrylate monomers, and combining low-polarity acrylate monomers and high-polarity acrylates to synergistically adjust the crystallization behavior of long side chain acrylate monomers, the resulting pressure-sensitive adhesive composition has a temperature-driven viscosity transition and exhibits significant viscosity changes near human body temperature. It is particularly suitable for application scenarios that require temperature-responsive viscosity, such as the load matrix of wearable devices.

[0023] The polypropylene glycol diol is dehydrated, and reacted with different diisocyanates under the action of a catalyst to obtain an isocyanate-terminated polyurethane prepolymer, and a hydroxy (meth) acrylate monomer is further added to react to obtain a polyurethane prepolymer partially terminated with isocyanate and partially terminated with acrylate. Finally, the polyurethane prepolymer containing a portion of isocyanate groups and a portion of (meth) acrylate groups is reacted with small molecule alcohols to obtain a stable photocurable polypropylene glycol type polyurethane prepolymer.

[0024] The preparation process of the present invention does not require the use of volatile organic solvents, which meets the current trend of green and environmentally friendly preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Example 1; Figure 2 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Example 2; Figure 3 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Example 3; Figure 4 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Example 4; Figure 5 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Comparative Example 1; Figure 6 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Comparative Example 2; Figure 7 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Comparative Example 3; Figure 8 This is the GPC curve of the photocurable polypropylene glycol type polyurethane prepolymer prepared in Comparative Example 4; Figures 1 to 8 They have similar molecular weight and dispersity. DETAILED DESCRIPTION

[0026] All raw materials in the examples can be obtained from commercial sources. The low-polarity acrylate monomer is preferably isooctyl acrylate; The high polarity acrylate is preferably hydroxyethyl acrylate; The long side chain acrylate monomer is preferably a combination of lauryl acrylate and octadecyl acrylate; The small molecule alcohol includes one of methanol, ethanol, isopropanol and isooctyl alcohol, preferably methanol; The hydroxy(meth)acrylate comprises one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxybutyl acrylate, preferably hydroxyethyl acrylate; The diisocyanate comprises one of aliphatic diisocyanates such as isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, m-xylylene diisocyanate, aromatic diisocyanates such as toluene diisocyanate, and diphenylmethane diisocyanate, preferably isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, m-xylylene diisocyanate and diphenylmethane diisocyanate; The polyether diol is a polypropylene glycol diol having a molecular weight of 1000-4000, preferably polypropylene glycol 1000; The photoinitiator includes TPO, TPO-L (a highly efficient liquid universal UV photoinitiator with good solubility), CB-1, photoinitiator 184 (also known as HCPK), and TPO (the main chemical component of the present invention is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, which has a wide absorption spectrum, an effective absorption peak of 350-400nm, and absorption to about 420nm); The antioxidant is one of 2,6-di-tert-butyl-p-cresol, hydroquinone and antioxidant 1010, preferably 2,6-di-tert-butyl-p-cresol.

[0027] Example 1 An optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition at body temperature is prepared by the following steps: 1) Raw material preparation: Raw materials are weighed according to the formula, wherein a photocurable polypropylene glycol type 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 added to a three-necked flask, then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and 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; the temperature was further cooled to 60°C, 0.048 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a polyurethane prepolymer containing part of the isocyanate group-terminated and part of the acrylate group-terminated; The polyurethane prepolymer containing part of isocyanate groups and part of acrylate groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0028] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.4 kg mol -1 , with a weight average molecular weight of 7.5 kg mol -1 , the dispersion is 1.7, and its GPC curve is as follows Figure 1 shown.

[0029] 2) At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, 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 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0030] The initial tack of the obtained transparent pressure-sensitive adhesive at 23°C is 0, the initial tack at 37°C is 18, and the transmittance is 90%, as shown in Table 1, reflecting the characteristics of body temperature-driven viscosity transition and optical transparency.

[0031] It exhibits significant viscosity changes near human body temperature and is suitable for application scenarios such as load substrates for wearable devices that require temperature-responsive viscosity.

[0032] Example 2 This embodiment provides an optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition. Other raw materials and proportions are the same as those in Example 1, except that the preparation of the photocurable polypropylene glycol type polyurethane prepolymer is slightly different, wherein: 1) A photocurable polypropylene glycol type polyurethane prepolymer is prepared according to the following method, except that there is no reaction step with a small molecule alcohol compared to step 1) of Example 1, and the amount of hydroxyethyl acrylate added is different: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and added to a three-necked flask, then cooled to 70 °C, 0.05 wt% of an organic tin catalyst was added, and 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 cooled to 60 °C, 0.12 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0033] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.6 kg mol -1 , with a weight average molecular weight of 7.5 kg mol -1 , the dispersion is 1.6, and the GPC curve is as follows Figure 2 .

[0034] 2) An optically transparent pressure-sensitive adhesive composition capable of tack-induced viscosity transition driven by body temperature is prepared according to the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, 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 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0035] The initial tack of the obtained transparent pressure-sensitive adhesive at 23°C is 0, the initial tack at 37°C is 11, and the transmittance is 91%, as shown in Table 1, reflecting the characteristics of body temperature-driven viscosity transition and optical transparency.

[0036] It exhibits significant viscosity changes near human body temperature and is suitable for application scenarios such as load substrates for wearable devices that require temperature-responsive viscosity.

[0037] Example 3 This embodiment provides an optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition. Other raw materials and proportions are the same as those in Example 1, except that the preparation of the photocurable polypropylene glycol type polyurethane prepolymer is slightly different, wherein: 1) A photocurable polypropylene glycol type polyurethane prepolymer, the amount of the organic tin catalyst added is different from that in step 1) of Example 1, and is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask, then cooled to 70°C, 0.01 wt% of an organic tin catalyst was added, and 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; then the temperature was cooled to 60°C, 0.048 mol of hydroxyethyl acrylate was added and further reacted for 2 h to obtain a polyurethane prepolymer containing partly isocyanate-terminated groups and partly acrylate-terminated groups; The polyurethane prepolymer containing part of isocyanate groups and part of acrylate groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0038] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.5 kg mol -1 , with a weight average molecular weight of 7.3 kg mol -1 , the dispersion is 1.6, and the GPC curve is as follows Figure 3 .

[0039] 2) An optically transparent pressure-sensitive adhesive composition capable of tack-induced viscosity transition driven by body temperature is prepared by the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, 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 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0040] The initial tack of the obtained transparent pressure-sensitive adhesive at 23°C is 0, the initial tack at 37°C is 22, and the transmittance is 91%, as shown in Table 1, reflecting the characteristics of body temperature-driven viscosity transition and optical transparency.

[0041] It exhibits significant viscosity changes near human body temperature and is suitable for application scenarios such as load substrates for wearable devices that require temperature-responsive viscosity.

[0042] Example 4 This embodiment provides an optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity change. Other raw materials and proportions are the same as those in Example 1, except that 1) A photocurable polypropylene glycol type polyurethane prepolymer, the amount of the organic tin catalyst added is different from that in Example 2, and there is no reaction step with a small molecule alcohol, and it is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask, then cooled to 70°C, 0.01 wt% of an organic tin catalyst was added, and then 0.16 mol of diphenylmethane diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate group-terminated polyurethane prepolymer was obtained; then, the temperature was cooled to 60°C, 0.12 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0043] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.6 kg mol -1 , with a weight average molecular weight of 7.4 kg mol -1 , the dispersion is 1.6, and the GPC curve is as follows Figure 4 .

[0044] 2) An optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition by body temperature, prepared according to the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, stirred and degassed at a speed of 300 r / min for 10 min to form a mixed acrylate monomer; subsequently, 20 g of the prepared photocurable polypropylene glycol type polyurethane prepolymer, 1 g of TPO, and 5 g of 2,6-di-tert-butyl-p-cresol were added to a stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0045] The initial tack of the obtained transparent pressure-sensitive adhesive at 23°C is 0, the initial tack at 37°C is 9, and the transmittance is 91%, as shown in Table 1, reflecting the characteristics of body temperature-driven viscosity transition and optical transparency.

[0046] It exhibits significant viscosity changes near human body temperature and is suitable for application scenarios such as load substrates for wearable devices that require temperature-responsive viscosity.

[0047] Comparative Example 1 This comparative example provides a transparent pressure-sensitive adhesive composition, and the other raw materials and proportions are the same as those in Example 1, except that: 1) A photocurable polypropylene glycol type polyurethane prepolymer, which is different from the diisocyanate raw material in step 1) of Example 1, is isophorone diisocyanate and is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask, then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and 0.16 mol of isophorone diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained; then, the temperature was cooled to 60°C, 0.048 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a polyurethane prepolymer containing partly isocyanate-terminated groups and partly acrylate-terminated groups; The polyurethane prepolymer containing part of isocyanate groups and part of acrylate groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0048] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.3 kg mol -1 , with a weight average molecular weight of 6.7 kg mol -1 , the dispersion is 1.6, and the GPC curve is as follows Figure 5 .

[0049] 2) A transparent pressure-sensitive adhesive composition is prepared according to the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, stirred and degassed at a speed of 300 r / min for 10 min to form a mixed acrylate monomer; then 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0050] The initial tack of the obtained transparent pressure-sensitive adhesive at 23°C is 25, the initial tack at 37°C is 24, and the transmittance is 92%, as shown in Table 1. It has the characteristics of optical transparency, but does not have the characteristic of viscosity transition driven by body temperature.

[0051] Comparative Example 2 This comparative example provides a transparent pressure-sensitive adhesive composition, and the other raw materials and proportions are the same as those in Example 1, except that 1) Photocurable polypropylene glycol type polyurethane prepolymer, the diisocyanate raw material is different, isophorone diisocyanate, and the amount of hydroxyethyl acrylate added is different, and there is no reaction step with small molecule alcohol, and it is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask. The temperature was then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and 0.16 mol of isophorone diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was cooled to 60°C, 0.12 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

[0052] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 3.5 kg mol -1 , with a weight average molecular weight of 6.0 kg mol -1 , the dispersion is 1.7, and the GPC curve is as follows Figure 6 .

[0053] 2) A transparent pressure-sensitive adhesive composition is prepared according to the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, stirred and degassed at a speed of 300 r / min for 10 min to form a mixed acrylate monomer; then 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0054] The obtained transparent pressure-sensitive adhesive has an initial tack of 7 at 23°C and 7 at 37°C, and a transmittance of 92%, as shown in Table 1. It has the characteristics of optical transparency, but does not have the characteristics of body temperature-driven viscosity transition, and has low viscosity.

[0055] Comparative Example 3 This comparative example provides a transparent pressure-sensitive adhesive composition, and other raw materials and proportions are the same as those in Example 1, except that: 1) A photocurable polypropylene glycol type polyurethane prepolymer, wherein the diisocyanate raw material is different from that in step 1 of Example 1, and is dicyclohexylmethane 4,4'-diisocyanate; the preparation is carried out according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask, then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and 0.16 mol of dicyclohexylmethane 4,4'-diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was cooled to 60°C, 0.048 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a polyurethane prepolymer containing partly isocyanate-terminated groups and partly acrylate-terminated groups. The polyurethane prepolymer containing part of isocyanate groups and part of acrylate groups was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0056] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 5.5 kg mol -1 , with a weight average molecular weight of 9.5 kg mol -1 , the dispersion is 1.7, and the GPC curve is as follows Figure 7 .

[0057] 2) A transparent pressure-sensitive adhesive composition is prepared according to the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to a stirring tank, 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 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 stirring tank, stirred and degassed at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0058] The initial tack at 23°C and 37°C was 19 and 24, respectively, and the transmittance was 92%, as shown in Table 1. The transparent pressure-sensitive adhesive had the characteristics of optical transparency, but did not have the characteristics of body temperature-driven viscosity transition and had low viscosity.

[0059] Comparative Example 4 This comparative example provides a transparent pressure-sensitive adhesive composition, and other raw materials and proportions are the same as those in Example 1, except that: 1) A photocurable polypropylene glycol type polyurethane prepolymer, the diisocyanate raw material is different from that in step 1 of Example 1, the amount of hydroxyethyl acrylate added is different, and there is no reaction step of small molecule alcohol, and it is prepared according to the following steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask, then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and then 0.16 mol of dicyclohexylmethane 4,4'-diisocyanate was slowly added through an addition funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained; then, the temperature was cooled to 60°C, 0.12 mol of hydroxyethyl acrylate was added and further reacted for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

[0060] The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 5.1 kg mol -1 , with a weight average molecular weight of 8.3 kg mol -1 , the dispersion is 1.6, and the GPC curve is as follows Figure 8 .

[0061] 2) A transparent pressure-sensitive adhesive composition and a preparation method thereof, comprising the following steps: At 40°C, 5 g of lauryl acrylate and 35 g of octadecyl acrylate were fully melted and mixed, and 20 g of isooctyl acrylate and 20 g of hydroxyethyl acrylate were added to the stirring tank and continued to mix and stir, degas and mix at a speed of 300 r / min for 10 min to form a mixed acrylate monomer; then 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 stirring tank and stirred to degas and mix thoroughly at a speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0062] The obtained transparent pressure-sensitive adhesive has an initial tack of 0 at 23°C, an initial tack of 3 at 37°C, and a transmittance of 91%, as shown in Table 1. It has the characteristics of optical transparency, weak body temperature-driven viscosity transition, and low viscosity.

[0063] Performance testing Adhesion performance test: The transparent pressure-sensitive adhesive composition in each embodiment and comparative example is coated on a PET film containing silicone oil and cured using a 365 nm LED cold light source. After curing for 2 minutes, an adhesive film is obtained. The initial adhesion of the adhesive film is tested by the inclined rolling ball method at different temperatures. The larger the ball number, the better the viscosity.

[0064] Optical performance test: Determine the film transmittance through the haze instrument refer to Figure 1-8 , the photocurable polypropylene glycol type polyurethane prepolymer has similar molecular weight and dispersity, proving a stable synthesis process.

[0065] Combining the optically transparent pressure-sensitive adhesives in Table 1, 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 grade applications. Examples 1-4 all show more significant temperature response initial adhesion changes compared to the comparative examples, and Example 3 shows the highest initial adhesion near body temperature.

[0066] In summary, the photocurable polypropylene glycol type polyurethane prepolymer changes the interaction between the polyurethane and acrylate monomers, and is combined with low-polarity acrylate monomers and high-polarity acrylates to synergistically adjust the crystallization behavior of the long side chain acrylate monomers. The obtained 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 application scenarios that require temperature-responsive viscosity, such as the load matrix of wearable devices.

[0067] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An optically transparent pressure-sensitive adhesive composition capable of driving viscosity transition at body temperature, characterized in that Comprise the following components in parts by weight: 10-30 parts of photocurable polypropylene glycol type 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, 2-5 parts of antioxidant, wherein: The obtained photocurable polypropylene glycol type polyurethane prepolymer has a number average molecular weight of 4.4-4.6 kg mol -1 , weight average molecular weight is 7.3-7.5 kg mol -1 , the dispersion is 1.

7.

2. An optically transparent pressure-sensitive adhesive composition capable of temperature-driven viscosity transition according to claim 1, characterized in that : The low-polarity acrylate monomer is isooctyl acrylate; The high polarity acrylate is hydroxyethyl acrylate; The long side chain acrylate monomer is a composition of lauryl acrylate and octadecyl acrylate; 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 capable of temperature-driven viscosity transition according to claim 1 or 2, characterized in that : It includes the following steps: At 40-50° C., the long side chain acrylate monomer is fully melted and mixed according to the formula amount, and then the low polarity acrylate monomer and the high polarity acrylate monomer are added into a stirring tank for mixing and stirring, and degassing and mixing are performed at a stirring speed of 300 r / min for 10 min to form a mixed acrylate monomer; Subsequently, a photocurable polypropylene glycol type polyurethane prepolymer, a photoinitiator and an antioxidant were added into a stirring tank for stirring, degassing and thorough mixing at a stirring speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

4. A photocurable polypropylene glycol type polyurethane prepolymer according to claim 1, characterized in that: The method comprises the following steps: Dehydrate 0.1 mol of polypropylene glycol with a molecular weight of 1000-4000 at 110°C for 2 h, then cool to 70°C, add 0.16 mol of diisocyanate, and react for 3-6 h under the catalysis of 0.01-0.05 wt% of organic tin to obtain an isocyanate group-terminated polyurethane prepolymer; Subsequently, the temperature is naturally lowered to 60° C., and 0.048-0.12 mol of hydroxy(meth)acrylate is added for further reaction for 1-2 h to obtain the photocurable polypropylene glycol type polyurethane prepolymer, wherein the hydroxy(meth)acrylate comprises one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate.

5. The photocurable polypropylene glycol type polyurethane prepolymer according to claim 4, characterized in that When the addition amount of hydroxy (meth) acrylate is 0.048 mol, a polyurethane prepolymer containing partly isocyanate group-terminated and partly acrylate group-terminated is obtained, and further reacts with 0.072 mol of small molecule alcohol to obtain the photocurable polypropylene glycol type polyurethane, wherein the small molecule alcohol is one of methanol, ethanol, isopropanol, and isooctyl alcohol.

6. The photocurable polypropylene glycol type polyurethane prepolymer according to claim 4, characterized in that : The diisocyanate comprises one of the aliphatic diisocyanates of isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, and meta-phenylenediisocyanate, or one of the aromatic diisocyanates of toluene diisocyanate and diphenylmethane diisocyanate; and the isocyanate index (R value) is 1.5-2.

0.

7. A method for preparing a photocurable polypropylene glycol type polyurethane prepolymer according to any one of claims 4 to 6, characterized in that : Follow these steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and added to a three-necked flask, then cooled to 70 °C, 0.05 wt% of an organic tin catalyst was added, and 0.16 mol of m-xylylene diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained; then, the temperature was cooled to 60 °C, 0.048 mol of hydroxyethyl acrylate was added and reacted for further 2 h to obtain a polyurethane prepolymer containing partly isocyanate-terminated groups and partly acrylate-terminated groups; or, 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110 °C for 2 h and added to a three-necked flask, then cooled to 70 °C, 0.01 wt% of an organic tin catalyst was added, and 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 cooled to 60 °C, 0.048 mol of hydroxyethyl acrylate was added and further reacted for 2 h to obtain a polyurethane prepolymer containing partly isocyanate-terminated groups and partly acrylate-terminated groups; The polyurethane prepolymer containing part of the isocyanate group-terminated and part of the acrylate group-terminated was reacted with 0.072 mol of methanol for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

8. A method for preparing a photocurable polypropylene glycol type polyurethane prepolymer according to any one of claims 4 to 6, characterized in that : Follow these steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask. The temperature was then cooled to 70°C, 0.05 wt% of an organic tin catalyst was added, and 0.16 mol of m-xylylene diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was cooled to 60°C, 0.12 mol of hydroxyethyl acrylate was added and the reaction was further carried out for 2 h to obtain a photocurable polypropylene glycol-type polyurethane prepolymer.

9. A method for preparing a photocurable polypropylene glycol type polyurethane prepolymer according to any one of claims 4 to 6, characterized in that : Follow these steps: 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and added to a three-necked flask. The temperature was cooled to 70°C, 0.01 wt% of an organic tin catalyst was added, and then 0.16 mol of diphenylmethane diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate group-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was cooled to 60°C, 0.12 mol of hydroxyethyl acrylate was added and the reaction was further reacted for 2 h to obtain a photocurable polypropylene glycol type polyurethane prepolymer.

10. An optically transparent pressure-sensitive adhesive composition capable of body temperature-driven viscosity transition as described in claim 1 or 2, for use in scenarios where the load substrate of a wearable device requires temperature-responsive viscosity.

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